Oracle sql & plsql

Tables Used in the Course
Three main tables are used in this course:
Three main tables are used in this course:
–
– EMP table
EMP table
–
– DEPT table
DEPT table


The EMP Table
EMP
EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO
--------- ---------- --------- --------- --------- --------- --------- ---------
7839 KING PRESIDENT 17-NOV-81 5000 10
7698 BLAKE MANAGER 7839 01-MAY-81 2850 30
7782 CLARK MANAGER 7839 09-JUN-81 1500 10
7566 JONES MANAGER 7839 02-APR-81 2975 20
7654 MARTIN SALESMAN 7698 28-SEP-81 1250 1400 30
7499 ALLEN SALESMAN 7698 20-FEB-81 1600 300 30
7844 TURNER SALESMAN 7698 08-SEP-81 1500 0 30
7900 JAMES CLERK 7698 03-DEC-81 950 30
7521 WARD SALESMAN 7698 22-FEB-81 1250 500 30
7902 FORD ANALYST 7566 03-DEC-81 3000 20
7369 SMITH CLERK 7902 17-DEC-80 800 20
7788 SCOTT ANALYST 7566 09-DEC-82 3000 20
7876 ADAMS CLERK 7788 12-JAN-83 1100 20
7934 MILLER CLERK 7782 23-JAN-82 1300 10

Primary key Foreign key Foreign key


DEPT Tables

DEPT
DEPTNO DNAME LOC
--------- -------------- ----------
10 ACCOUNTING NEW YORK
20 RESEARCH DALLAS
30 SALES CHICAGO
40 OPERATIONS BOSTON

Primary key


Writing Basic
SQL Statements


Capabilities of SQL SELECT
Statements
Restriction Projection

Table 1 Table 1
Join

Table 1 Table 2


Basic SELECT Statement

SELECT [DISTINCT] {*, column [alias],...}
FROM table
[WHERE condition(s)]
[GROUP BY group_by_expression]
[ORDER BY column];

–
– SELECT identifies the columns to be displayed.
SELECT identifies the columns to be displayed.
–
– FROM identifies the table that contains the columns.
FROM identifies the table that contains the columns.


Writing SQL Statements

–
– SQL statements are not case sensitive.
SQL statements are not case sensitive.
–
– SQL statements can be on one or
SQL statements can be on one or
more lines.
more lines.
–
– Keywords cannot be abbreviated or split across lines.
Keywords cannot be abbreviated or split across lines.
–
– Clauses are usually placed on
Clauses are usually placed on
separate lines.
separate lines.
–
– Tabs and indents are used to enhance readability.
Tabs and indents are used to enhance readability.


Retrieving All Columns
from a Table
DEPT Retrieve all
DEPTNO DNAME LOC
columns from the
10 ACCOUNTING NEW YORK DEPT table
20 RESEARCH DALLAS
30 SALES CHICAGO

DEPT
DEPTNO DNAME LOC

20 RESEARCH DALLAS
30 SALES CHICAGO

All columns are displayed

Selecting All Columns

SQL> SELECT *
2 FROM dept;

DEPTNO DNAME LOC
--------- -------------- -------------
20 RESEARCH DALLAS
30 SALES CHICAGO


Creating a Projection on a Table
DEPT
DEPTNO DNAME LOC Retrieve DEPTNO
and LOC columns
20 RESEARCH DALLAS
from the DEPT
30 SALES CHICAGO table

DEPT
DEPTNO LOC

10 NEW YORK
20 DALLAS
30 CHICAGO
40 BOSTON
Only two columns are displayed

Selecting Specific Columns

SQL> SELECT deptno, loc
2 FROM dept;

DEPTNO LOC
--------- -------------
10 NEW YORK
20 DALLAS
30 CHICAGO
40 BOSTON


Default Column Justification

Character Date Number
left justified left justified right justified

EMP
ENAME HIREDATE SAL
---------- --------- ---------
KING 17-NOV-81 5000
BLAKE 01-MAY-81 2850
CLARK 09-JUN-81 2450
JONES 02-APR-81 2975
MARTIN 28-SEP-81 1250
ALLEN 20-FEB-81 1600
...
14 rows selected.


Arithmetic Expressions
Create expressions on NUMBER and DATE data
Create expressions on NUMBER and DATE data
types by using arithmetic operators.
types by using arithmetic operators.

Operator Description

+ Add

- Subtract

* Multiply

/ Divide


Using Arithmetic Operators

SQL> SELECT ename, sal, sal+300
2 FROM emp;

ENAME SAL SAL+300
---------- --------- ---------
KING 5000 5300
BLAKE 2850 3150
CLARK 2450 2750
JONES 2975 3275
MARTIN 1250 1550
ALLEN 1600 1900
...
14 rows selected.


Using Arithmetic Operators on
Multiple Columns

SQL> SELECT grade, hisal-losal
2 FROM salgrade;

GRADE HISAL-LOSAL
--------- -----------
1 500
2 199
3 599
4 999
5 6998


Operator Precedence

/ + _
*
–
– Multiplication and division take priority over addition
Multiplication and division take priority over addition
and subtraction.
and subtraction.
–
– Operators of the same priority are evaluated from left to
Operators of the same priority are evaluated from left to
right.
right.
–
– Parentheses are used to force prioritized evaluation
Parentheses are used to force prioritized evaluation
and to clarify statements.
and to clarify statements.


Operator Precedence

SQL> SELECT ename, sal, 12*sal+100
2 FROM emp;

ENAME SAL 12*SAL+100
---------- --------- ----------
KING 5000 60100
BLAKE 2850 34300
CLARK 2450 29500
JONES 2975 35800
MARTIN 1250 15100
ALLEN 1600 19300
...
14 rows selected.


Using Parentheses

SQL> SELECT ename, sal, 12*(sal+100)
2 FROM emp;

ENAME SAL 12*(SAL+100)
---------- --------- -----------
KING 5000 61200
BLAKE 2850 35400
CLARK 2450 30600
JONES 2975 36900
MARTIN 1250 16200
...
14 rows selected.


Defining a Column Alias

–
– Renames a column heading
Renames a column heading
–
– Is useful with calculations
Is useful with calculations
–
– Immediately follows column name; optional AS
Immediately follows column name; optional AS
keyword between column name and alias
keyword between column name and alias
–
– Requires double quotation marks if it is case sensitive
Requires double quotation marks if it is case sensitive
or contains spaces or special characters
or contains spaces or special characters


Using Column Aliases

SQL> SELECT ename AS name, sal salary
2 FROM emp;

NAME SALARY
------------- ---------
KING 5000
BLAKE 2850
CLARK 2450
JONES 2975
...
14 rows selected.


Using Column Aliases

SQL> SELECT ename "Name",
2 sal*12 "Annual Salary"
3 FROM emp;

Name Annual Salary
------------- -------------
KING 60000
BLAKE 34200
CLARK 29400
...
14 rows selected.


Concatenation Operator

–
– Concatenates columns or character strings to other
Concatenates columns or character strings to other
columns
columns
–
– Is represented by two vertical bars ||
Is represented by two vertical bars ||
–
– Creates a result column that is a character expression
Creates a result column that is a character expression


Using the Concatenation Operator

SQL> SELECT ename||job AS "Employees"
2 FROM emp;

Employees
-------------------
KINGPRESIDENT
BLAKEMANAGER
CLARKMANAGER
JONESMANAGER
MARTINSALESMAN
ALLENSALESMAN
...
14 rows selected.


Literals

–
– A literal is a constant value of character, expression, or
A literal is a constant value of character, expression, or
number that can be included in the SELECT list.
number that can be included in the SELECT list.
–
– Date and character literal values must be enclosed in
Date and character literal values must be enclosed in
single quotation marks.
–
– Each character string is output once for each row
Each character string is output once for each row
returned.
returned.


Using Literal Character Strings

SQL> SELECT ename||' is a '||job AS
2 "Employee Details"
3 FROM emp;

Employee Details
-------------------------
KING is a PRESIDENT
BLAKE is a MANAGER
CLARK is a MANAGER
JONES is a MANAGER
MARTIN is a SALESMAN
...
14 rows selected.


Duplicate Rows
The default display of queries is all rows, including
The default display of queries is all rows, including
duplicate rows.
duplicate rows.

SQL> SELECT deptno
2 FROM emp;

DEPTNO
---------
10
30
10
20
..
14 rows selected.


Eliminating Duplicate Rows
Eliminate duplicate rows by using the DISTINCT
Eliminate duplicate rows by using the DISTINCT
keyword in the SELECT clause.
keyword in the SELECT clause.

SQL> SELECT DISTINCT deptno
2 FROM emp;

DEPTNO
---------
10
20
30


Restricting and Sorting Data


Limiting Rows by Using a Restriction

EMP
EMPNO ENAME JOB ... DEPTNO
Retrieve all
7839 KING PRESIDENT 10 employees
7698 BLAKE MANAGER 30 in department 10
7782 CLARK MANAGER 10
7566 JONES MANAGER 20
...

EMP
EMPNO ENAME JOB ... DEPTNO

7839 KING PRESIDENT 10
7934 MILLER CLERK 10


Using the WHERE Clause

SQL> SELECT ename, job, deptno
2 FROM emp
3 WHERE deptno=10;

ENAME JOB DEPTNO
---------- --------- ---------
KING PRESIDENT 10
CLARK MANAGER 10
MILLER CLERK 10


Character Strings and Dates

–
– Character strings and date values are enclosed in
Character strings and date values are enclosed in
–
– Character values are case sensitive and date values
Character values are case sensitive and date values
are format sensitive.
are format sensitive.
–
– Default date format is DD-MON-YY.
Default date format is DD-MON-YY.

SQL> SELECT ename, job, deptno, hiredate
2 FROM emp
3 WHERE ename = 'JAMES';


Comparison Operators

Operator Meaning

= Equal to

> Greater than

>= Greater than or equal to

< Less than

<= Less than or equal to

<> Not equal to


Using the Comparison Operators
with Another Column

SQL> SELECT ename, sal, comm
2 FROM emp
3 WHERE sal<=comm;

ENAME SAL COMM
---------- --------- ---------
MARTIN 1250 1400


Using the Comparison Operators
with Characters

SQL> SELECT ename, mgr
2 FROM emp
3 WHERE ename='SMITH';

ENAME MGR
---------- ---------
SMITH 7902


Other SQL Comparison Operators

Operator Meaning

BETWEEN Between two values (inclusive)
...AND...

IN(list) Match any of a list of values

LIKE Match a character pattern

IS NULL Is a null value


Using the BETWEEN Operator
Use the BETWEEN operator to display rows based on
Use the BETWEEN operator to display rows based on
a range of values.
a range of values.

SQL> SELECT ename, sal
2 FROM emp
3 WHERE sal BETWEEN 1000 AND 1500;

ENAME SAL
---------- --------- Lower Higher
MARTIN 1250 limit limit
TURNER 1500
WARD 1250
ADAMS 1100
MILLER 1300


Using the IN Operator
Use the IN operator to test for values in a list.
Use the IN operator to test for values in a list.

SQL> SELECT empno, ename, sal, mgr
2 FROM emp
3 WHERE mgr IN (7902, 7566, 7788);

EMPNO ENAME SAL MGR
--------- ---------- --------- ---------
7902 FORD 3000 7566
7369 SMITH 800 7902
7788 SCOTT 3000 7566
7876 ADAMS 1100 7788


Using the IN Operator with Strings
Use the IN operator to test for values in a list of
Use the IN operator to test for values in a list of
strings.
strings.

SQL> SELECT ename, deptno, hiredate
2 FROM emp
3 WHERE ename IN ('BLAKE','MARTIN');

ENAME DEPTNO HIREDATE
---------- --------- ---------
BLAKE 30 01-MAY-81
MARTIN 30 28-SEP-81


Using the LIKE Operator

–
– Use the LIKE operator to perform wildcard searches of
Use the LIKE operator to perform wildcard searches of
valid search string values.
valid search string values.
–
– Search conditions can contain either literal characters
Search conditions can contain either literal characters
or numbers.
or numbers.
% denotes zero or many characters
% denotes zero or many characters
_ denotes one character
_ denotes one character

SQL> SELECT ename
2 FROM emp
3 WHERE ename LIKE 'S%';


Using the LIKE Operator
• You can combine pattern matching
• You can combine pattern matching
characters.
characters.

SQL> SELECT ename
2 FROM emp
3 WHERE ename LIKE '_A%';

ENAME
----------
MARTIN
JAMES
WARD

• Use the ESCAPE identifier to search for
• Use the ESCAPE identifier to search for
% or _.
% or _.

Using the IS NULL Operator

Test for null values with the IS NULL operator.
Test for null values with the IS NULL operator.

2 FROM emp
3 WHERE mgr IS NULL;

ENAME MGR
---------- ---------
KING


Logical Operators

Operator Meaning

AND Returns TRUE if both component
conditions are TRUE
OR Returns TRUE if either component
condition is TRUE

NOT Returns TRUE if the following
condition is FALSE


Using the AND Operator
AND requires both conditions to be TRUE.

SQL> SELECT empno, ename, job, sal
2 FROM emp
3 WHERE sal>=1100
4 AND job='CLERK';

EMPNO ENAME JOB SAL
--------- ---------- --------- ---------
7876 ADAMS CLERK 1100
7934 MILLER CLERK 1300



SQL> SELECT ename, mgr, sal,deptno
2 FROM emp
3 WHERE sal>1000
4 AND deptno = 10;

ENAME MGR SAL DEPTNO
---------- --------- --------- ---------
KING 5000 10
CLARK 7839 2450 10
MILLER 7782 1300 10


Using the OR Operator

OR requires either condition to be TRUE.
SQL> SELECT empno, ename, job, sal
2 FROM emp
3 WHERE sal>=2000
4 OR job='CLERK';
EMPNO ENAME JOB SAL
--------- ---------- --------- ---------
7839 KING PRESIDENT 5000
7698 BLAKE MANAGER 2850
7566 JONES MANAGER 2975
7900 JAMES CLERK 950
7902 FORD ANALYST 3000
...
10 rows selected.

Using the OR Operator

SQL> SELECT ename, deptno, mgr
2 FROM emp
3 WHERE deptno = 10
4 OR mgr = 7839;

ENAME DEPTNO MGR
---------- -------- ---------
KING 10
BLAKE 30 7839
CLARK 10 7839
JONES 20 7839
MILLER 10 7782


Using the NOT Operator

SQL> SELECT ename, job
2 FROM emp
3 WHERE job NOT IN ('CLERK','MANAGER','ANALYST');

ENAME JOB
---------- ---------
KING PRESIDENT
MARTIN SALESMAN
ALLEN SALESMAN
TURNER SALESMAN
WARD SALESMAN



SQL> SELECT empno,ename,deptno,mgr
2 FROM emp
3 WHERE mgr NOT LIKE '78%';

EMPNO ENAME DEPTNO MGR
--------- ---------- --------- ---------
7654 MARTIN 30 7698
7499 ALLEN 30 7698
...
...
7902 FORD 20 7566
7369 SMITH 20 7902
...
10 rows selected.



SQL> SELECT empno, sal, mgr
2 FROM emp
3 WHERE sal NOT BETWEEN 1000 AND 1500;

EMPNO SAL MGR
--------- --------- ---------
7839 5000
7698 2850 7839
7782 2450 7839
7566 2975 7839
7499 1600 7698
7900 950 7698
7902 3000 7566
7369 800 7902
7788 3000 7566

9 rows selected.


SQL> SELECT ename, sal AS "Salary Before Commission",
2 comm
3 FROM emp
4 WHERE comm IS NOT NULL;

ENAME Salary Before Commission COMM
---------- ------------------------ ---------
MARTIN 1250 1400
ALLEN 1600 300
TURNER 1500 0
WARD 1250 500


Rules of Precedence

Order Evaluated Operator
1 All comparison
operators
2 NOT
3 AND
4 OR

Use parentheses to override rules of precedence.
Use parentheses to override rules of precedence.


Rules of Precedence

SQL> SELECT ename, job, sal
2 FROM emp
3 WHERE job='SALESMAN'
4 OR job='PRESIDENT'
5 AND sal>1500;

ENAME JOB SAL
---------- ------- ---------
KING PRESIDENT 5000
MARTIN SALESMAN 1250
ALLEN SALESMAN 1600
TURNER SALESMAN 1500
WARD SALESMAN 1250


Rules of Precedence
Use parentheses to force priority.
Use parentheses to force priority.
2 FROM emp
3 WHERE (job='SALESMAN'
4 OR job='PRESIDENT')
5 AND sal>1500;

ENAME JOB SAL
---------- --------- ---------
KING PRESIDENT 5000
ALLEN SALESMAN 1600


ORDER BY Clause
–
– Sort rows with the ORDER BY clause:
Sort rows with the ORDER BY clause:
ASC: ascending order, default
ASC: ascending order, default
DESC: descending order
DESC: descending order
–
– The ORDER BY clause comes last in the SELECT
The ORDER BY clause comes last in the SELECT
statement.
statement.

SQL> SELECT ename, job, deptno
2 FROM emp
3 ORDER BY deptno;
ENAME JOB DEPTNO
---------- --------- ---------
KING PRESIDENT 10
CLARK MANAGER 10
...
JONES MANAGER 20
SCOTT ANALYST 20
...
14 rows selected.

Sorting in Descending Order

SQL> SELECT ename, job, deptno, sal
2 FROM emp
3 ORDER BY sal DESC;

ENAME JOB DEPTNO SAL
---------- --------- --------- ---------
KING PRESIDENT 10 5000
FORD ANALYST 20 3000
SCOTT ANALYST 20 3000
JONES MANAGER 20 2975
BLAKE MANAGER 30 2850
CLARK MANAGER 10 2450
ALLEN SALESMAN 30 1600
...
14 rows selected.


Sorting by Column Alias

SQL> SELECT empno, ename, sal*12 annsal
2 FROM emp
3 ORDER BY annsal;

EMPNO ENAME ANNSAL
--------- ---------- ---------
7369 SMITH 9600
7900 JAMES 11400
7876 ADAMS 13200
7654 MARTIN 15000
7521 WARD 15000
7934 MILLER 15600
7844 TURNER 18000
...
14 rows selected.


Sorting by Multiple Columns
The order of an ORDER BY list is the order of the
The order of an ORDER BY list is the order of the
sort.
sort.

SQL> SELECT ename, deptno, sal
2 FROM emp
3 ORDER BY deptno, sal DESC;

ENAME DEPTNO SAL
---------- --------- ---------
KING 10 5000
CLARK 10 2450
MILLER 10 1300
FORD 20 3000
...
14 rows selected.


Sorting by a Column Not in the
SELECT List
SQL> SELECT ename, deptno
2 FROM emp
3 ORDER BY sal;

ENAME DEPTNO
---------- ---------
SMITH 20
JAMES 30
ADAMS 20
MARTIN 30
WARD 30
MILLER 10
...
14 rows selected.


Single-Row Number and Character
Functions


How a Function Works

Input Function Output

Performs
operation


Two Types of SQL Functions

Functions

Single-row Multiple-row
functions functions


Single-Row Functions

–
– Manipulate data items
Manipulate data items
–
– Accept arguments and return one value
Accept arguments and return one value
–
– Act on each row returned
Act on each row returned
–
– Return one result per row
Return one result per row
–
– Can modify the data type
Can modify the data type
–
– Can be nested
Can be nested


Single-Row Functions

Character Number

Single-row
functions

Conversion Date


Character Functions
Character
functions

Case conversion Character manipulation
functions functions

LOWER
UPPER
INITCAP


Case Conversion Functions
Convert the case for character strings
Convert the case for character strings

Function Result
LOWER('SQL Course') sql course
UPPER('SQL Course') SQL COURSE
INITCAP('SQL Course') Sql Course


Using Case Conversion Functions

Display the employee number, name, and department
Display the employee number, name, and department
number for employee Blake.
number for employee Blake.

SQL> SELECT empno, ename, deptno
2 FROM emp
3 WHERE ename = 'blake';
no rows selected

SQL> SELECT empno, ename, deptno
2 FROM emp
3 WHERE ename = UPPER('blake');

EMPNO ENAME DEPTNO
--------- ---------- ---------
7698 BLAKE 30


Using Case Conversion Functions
Display the employee name for all employees with an
Display the employee name for all employees with an
initial capital.
initial capital.

SQL> SELECT INITCAP(ename) as EMPLOYEE
2 FROM emp;

EMPLOYEE
----------
King
Blake
Clark
Jones
Martin
...
14 rows selected.


Number Functions

–
– ROUND: Rounds value to specified decimal
ROUND: Rounds value to specified decimal
ROUND(45.926, 2)
ROUND(45.926, 2)
45.93
45.93
–
– TRUNC: Truncates value to specified decimal
TRUNC: Truncates value to specified decimal
TRUNC(45.926, 2)
TRUNC(45.926, 2)
45.92
45.92
–
– MOD: Returns remainder of division
MOD: Returns remainder of division
MOD(1600, 300)
MOD(1600, 300)
100
100


Defining a Null Value
–
– A null is a value that is unavailable, unassigned,
A null is a value that is unavailable, unassigned,
unknown, or inapplicable.
unknown, or inapplicable.
–
– A null is not the same as zero or a blank space.
A null is not the same as zero or a blank space.

SQL> SELECT ename, job, comm
2 FROM emp;

ENAME JOB COMM
---------- --------- ---------
KING PRESIDENT
BLAKE MANAGER
...
TURNER SALESMAN 0
...
14 rows selected.


Null Values in Arithmetic
Expressions
Arithmetic expressions that contain a null value
Arithmetic expressions that contain a null value
evaluate to null.
evaluate to null.

SQL> SELECT ename NAME, 12*sal+comm
2 FROM emp;

NAME 12*SAL+COMM
---------- -----------
KING
BLAKE
CLARK
JONES
MARTIN 16400
...
14 rows selected.


Using the NVL Function

NVL (expr1, expr2)

Use the NVL function to force a value where a null
Use the NVL function to force a value where a null
would otherwise appear:
would otherwise appear:
–
– NVL can be used with date, character, and number
NVL can be used with date, character, and number
data types.
data types.
–
– Data types must match. For example:
Data types must match. For example:
NVL(comm,0)
NVL(comm,0)
NVL(hiredate,'01-JAN-97')
NVL(hiredate,'01-JAN-97')
NVL(job,'no job yet')
NVL(job,'no job yet'
yet')


Using the NVL Function to Handle
Null Values

SQL> SELECT ename, job, sal * 12 + NVL(comm,0)
2 FROM emp;

ENAME JOB SAL*12+NVL(COMM,0)
---------- --------- ------------------
KING PRESIDENT 60000
BLAKE MANAGER 34200
CLARK MANAGER 29400
JONES MANAGER 35700
MARTIN SALESMAN 16400
ALLEN SALESMAN 19500
TURNER SALESMAN 18000
...
14 rows selected.


Single-Row Date and Conversion
Functions


Working with Dates
–
– Oracle stores dates in an internal 7 byte numeric format:
Oracle stores dates in an internal 7 byte numeric format:
century, year, month, day, hours, minutes, seconds.
century, year, month, day, hours, minutes, seconds.
–
– The default date format is DD-MON-YY.
The default date format is DD-MON-YY.


SYSDATE

–
– Use SYSDATE to display the current date and time.
Use SYSDATE to display the current date and time.
–
– DUAL is a one-column, one-row table that is used as a
DUAL is a one-column, one-row table that is used as a
dummy table.
dummy table.

SQL> SELECT SYSDATE
2 FROM DUAL;

SYSDATE
---------
26-JAN-98


Default Date Formats

Columns that are defined as DATE are
Columns that are defined as DATE are
displayed as DD-MON-YY by default.
displayed as DD-MON-YY by default.

SQL> SELECT ename, hiredate
2 FROM emp

ENAME HIREDATE
---------- ---------
SMITH 17-DEC-80


Arithmetic with Dates
–
– Add or subtract a number to or from a date to obtain a date
Add or subtract a number to or from a date to obtain a date
value
value
–
– Subtract two dates to find the number of days between
Subtract two dates to find the number of days between
those dates
those dates


Using Arithmetic Operators
with Dates

SQL> SELECT ename, hiredate, hiredate+30 "NEW DATE"
2 FROM emp

ENAME HIREDATE NEW DATE
---------- --------- ---------
SMITH 17-DEC-80 16-JAN-81


Using SYSDATE in Calculations

Determine for how many weeks employees have
Determine for how many weeks employees have
worked
worked

SQL> SELECT ename, (SYSDATE-hiredate)/7
2 "WEEKS AT WORK"
3 FROM emp
4 WHERE deptno=10;

ENAME WEEKS AT WORK
---------- -------------
KING 844.94617
CLARK 867.94617
MILLER 835.37474


Explicit Data Type Conversion

TO_NUMBER TO_DATE

NUMBER CHARACTER DATE

TO_CHAR TO_CHAR


Modifying the Display Format of
Dates

Tuesday the 27th of January, 1998

27-JAN-98 January 27, 1998

01/27/98


TO_CHAR Function with Dates

TO_CHAR(date, 'fmfmt')

The format model:
The format model:
–
– Is case sensitive and must be enclosed in single
Is case sensitive and must be enclosed in single
quotation marks
quotation marks
–
– Can include any valid date format element
Can include any valid date format element
–
– Has an fm element to remove padded blanks or
Has an fm element to remove padded blanks or
suppress leading zeros
suppress leading zeros
–
– Is separated from the date value by a comma
Is separated from the date value by a comma


Date Format Model Elements

YYYY Full year in numbers

YEAR Year spelled out

MM 2-digit value for month

MONTH Full name of the month
3-letter abbreviation of the day
DY
of the week
DAY Full name of the day


Using the TO_CHAR Function with
Dates
SQL> SELECT ename, TO_CHAR(hiredate, 'Month DDth, YYYY')
2 AS HIREDATE
3 FROM emp
4 WHERE job='MANAGER';

ENAME HIREDATE
---------- --------------------
BLAKE May 01st, 1981
CLARK June 09th, 1981
JONES April 02nd, 1981


Dates

SQL> SELECT empno, TO_CHAR(hiredate, 'MM/YY') AS MONTH
2 FROM emp
3 WHERE ename='BLAKE';

EMPNO MONTH
--------- -----
7698 05/81


Dates

SQL> SELECT ename,
2 TO_CHAR(hiredate, 'fmDD Month YYYY') AS HIREDATE
3 FROM emp;

ENAME HIREDATE
---------- -----------------
KING 17 November 1981
BLAKE 1 May 1981
CLARK 9 June 1981
JONES 2 April 1981
MARTIN 28 September 1981
ALLEN 20 February 1981
...
14 rows selected.


Dates

SQL> SELECT ename, mgr, sal,TO_CHAR(hiredate,'YYYY-MON-DD')
2 AS HIREDATE
3 FROM emp
4 WHERE sal<1000
5 AND hiredate like '%80';

ENAME MGR SAL HIREDATE
---------- --------- --------- -----------
SMITH 7902 800 1980-DEC-17


Dates

SQL> SELECT empno,ename,deptno,TO_CHAR(hiredate,'MM-DD-YYYY')
2 AS HIREDATE
3 FROM emp
4 WHERE hiredate NOT LIKE '%81';

EMPNO ENAME DEPTNO HIREDATE
-------- ---------- --------- -----------
7369 SMITH 20 12-17-1980
7788 SCOTT 20 12-09-1982
7876 ADAMS 20 01-12-1983
7934 MILLER 10 01-23-1982


Dates
SQL> SELECT ename, job, deptno,
2 TO_CHAR(hiredate,'DD-MON-YYYY') AS HIRE_DATE
3 FROM emp
4 ORDER BY hiredate DESC;

ENAME JOB DEPTNO HIRE_DATE
---------- --------- --------- -----------
ADAMS CLERK 20 12-JAN-1983
SCOTT ANALYST 20 09-DEC-1982
MILLER CLERK 10 23-JAN-1982
JAMES CLERK 30 03-DEC-1981
FORD ANALYST 20 03-DEC-1981
KING PRESIDENT 10 17-NOV-1981
MARTIN SALESMAN 30 28-SEP-1981
...
14 rows selected.


Date Format Model Elements

• Time elements format the time portion of the date.
Time elements format the time portion of the date.

HH24:MI:SS AM 15:45:32 PM

DD "of" MONTH 12 of OCTOBER

ddspth fourteenth


Using Format Models to Display Time

SQL> SELECT TO_CHAR(SYSDATE,'HH24:MI:SS') TIME
2 FROM DUAL;

TIME
--------
13:55:46


TO_CHAR Function with Numbers
TO_CHAR(n,'fmt')
Use these formats with the TO_CHAR function to
Use these formats with the TO_CHAR function to
display a number value as a character:
display a number value as a character:

9 Represents a number
0 Forces a zero to be displayed
$ Places a floating dollar sign
L Uses the floating local currency symbol
. Prints a decimal point
, Places a thousand indicator


Numbers

SQL> SELECT TO_CHAR(sal,'$99,999') SALARY
2 FROM emp
3 WHERE ename = 'SCOTT';

SALARY
--------
$3,000

Thousand indicator
Dollar sign


Using the TO_NUMBER and
TO_DATE Functions
–
– Convert a character string to a number data type using the
Convert a character string to a number data type using the
TO_NUMBER function
TO_NUMBER function

TO_NUMBER(char)

• Convert a character string to a date data
• Convert a character string to a date data
type using the TO_DATE function
type using the TO_DATE function
TO_DATE(char[, 'fmt'])


Using the TO_NUMBER Function

SQL> SELECT TO_NUMBER('1000')+sal AS NEW_SALARY
2 FROM emp
3 WHERE ename = 'SCOTT';

NEW_SALARY
----------
4000


Date Functions
FUNCTION DESCRIPTION

MONTHS_BETWEEN Number of months
between two dates
ADD_MONTHS Adds calendar months to
date
NEXT_DAY Next day following the date
specified

LAST_DAY Last day of the month

ROUND Round off date

TRUNC Truncate date


Using Date Functions

Use the ADD_MONTHS function to add months to
Use the ADD_MONTHS function to add months to
a date.
a date.
SQL> SELECT ename, hiredate, ADD_MONTHS(hiredate, 6)
2 AS "+6 MONTHS"
3 FROM emp
4 WHERE ename='BLAKE';

ENAME HIREDATE +6 MONTHS
---------- --------- ---------
BLAKE 01-MAY-81 01-NOV-81


Nesting Functions
–
– Single-row functions can be nested to any level.
Single-row functions can be nested to any level.
–
– Nested functions are evaluated from the innermost level to
Nested functions are evaluated from the innermost level to
the outermost level.
the outermost level.

F3(F2(F1(col,arg1),arg2),arg3)
Step 1 = Result 1
Step 2 = Result 2
Step 3 = Result 3


Nesting Functions

Result 2
Result 1
SQL> SELECT ename,
2 NVL(TO_CHAR(mgr),'No Manager')
3 FROM emp
4 WHERE mgr IS NULL;

ENAME NVL(TO_CHAR(MGR),'NOMANAGER')
---------- -----------------------------
KING No Manager


Nesting Functions
SQL> SELECT MONTHS_BETWEEN
2 (TO_DATE('02-02-1995','MM-DD-YYYY'),
3 TO_DATE('01-01-1995','MM-DD-YYYY'))
4 "Months"
5 FROM DUAL;

Months
----------
1.03225806


Displaying Data
from Multiple Tables


Obtaining Data from Multiple Tables
Obtaining Data from Multiple Tables
EMP DEPT
EMPNO ENAME ... DEPTNO DEPTNO DNAME LOC
------ ----- ... ------ ------ ---------- --------
7839 KING ... 10 10 ACCOUNTING NEW YORK
7698 BLAKE ... 30 20 RESEARCH DALLAS
... 30 SALES CHICAGO
7934 MILLER ... 10 40 OPERATIONS BOSTON

EMPNO DEPTNO LOC
----- ------- --------
7839 10 NEW YORK
7698 30 CHICAGO
7782 10 NEW YORK
7566 20 DALLAS
7654 30 CHICAGO
7499 30 CHICAGO


Joining Tables
Use a join to query data from more than one table:
Use a join to query data from more than one table:

SELECT table1.column1, table2.column2
FROM table1, table2
WHERE Write the join condition in the WHERE clause.
table1.column1 = table2.column2;
– Write the join condition in the WHERE clause.
–
–
– Prefix the column name with the table name when the
Prefix the column name with the table name when the
same column name appears in more than one table.
same column name appears in more than one table.


Types of Joins

Equijoin Nonequijoin Self join
Equijoin Nonequijoin Self join


What Is an Equijoin?
EMP
EMPNO ENAME DEPTNO
------ ------- -------
... DEPT
7782 CLARK 10
DEPTNO DNAME LOC
------- ---------- --------
...
...

Links rows that satisfy a specified condition

WHERE emp.deptno=dept.deptno


Equijoin
EMP DEPT
EMPNO ENAME DEPTNO DEPTNO DNAME LOC
------ ------- ------- ------- ---------- --------
7839 KING 10 10 ACCOUNTING NEW YORK
7698 BLAKE 30 30 SALES CHICAGO
7782 CLARK 10 10 ACCOUNTING NEW YORK
7566 JONES 20 20 RESEARCH DALLAS
7654 MARTIN 30 30 SALES CHICAGO
7499 ALLEN 30 30 SALES CHICAGO
7844 TURNER 30 30 SALES CHICAGO
7900 JAMES 30 30 SALES CHICAGO
7521 WARD 30 30 SALES CHICAGO
7902 FORD 20 20 RESEARCH DALLAS
7369 SMITH 20 20 RESEARCH DALLAS
... ...
14 rows selected. 14 rows selected.

Foreign key Primary key

Retrieving Records
with an Equijoin

SQL> SELECT emp.empno, emp.ename, emp.deptno,
2 dept.deptno, dept.loc
3 FROM emp, dept
4 WHERE emp.deptno=dept.deptno;

EMPNO ENAME DEPTNO DEPTNO LOC
----- ------ ------ ------ ---------
7839 KING 10 10 NEW YORK
7698 BLAKE 30 30 CHICAGO
7782 CLARK 10 10 NEW YORK
7566 JONES 20 20 DALLAS
...
14 rows selected.


Qualifying Ambiguous
Column Names
–
– Use table prefixes to qualify column names that are in
Use table prefixes to qualify column names that are in
multiple tables.
multiple tables.
–
– Use table prefixes to improve performance.
Use table prefixes to improve performance.


Additional Search Conditions
EMP DEPT
EMPNO ENAME DEPTNO DEPTNO DNAME LOC
------ ------- ------- ------ --------- --------
7839 KING 10 10 ACCOUNTING NEW YORK
7698 BLAKE 30 30 SALES CHICAGO
7782 CLARK 10 10 ACCOUNTING NEW YORK
7566 JONES 20 20 RESEARCH DALLAS
7654 MARTIN 30 30 SALES CHICAGO
7499 ALLEN 30 30 SALES CHICAGO
7844 TURNER 30 30 SALES CHICAGO
7900 JAMES 30 30 SALES CHICAGO
... ...
14 rows selected. 14 rows selected.

WHERE emp.deptno=dept.deptno AND ename='KING'


Using Additional Search Conditions
with a Join

SQL> SELECT emp.empno, emp.ename, emp.deptno, dept.loc
2 FROM emp, dept;
3 WHERE emp.deptno = dept.deptno
4 AND emp.ename = 'KING';

EMPNO ENAME DEPTNO LOC
--------- ---------- --------- -------------
7839 KING 10 NEW YORK


Using Additional Search Conditions
with a Join

SQL> SELECT emp.ename, emp.job, dept.deptno, dept.dname
2 FROM emp, dept
3 WHERE emp.deptno=dept.deptno
4 AND emp.job IN ('MANAGER','PRESIDENT');

ENAME JOB DEPTNO DNAME
---------- --------- --------- --------------
KING PRESIDENT 10 ACCOUNTING
BLAKE MANAGER 30 SALES
CLARK MANAGER 10 ACCOUNTING
JONES MANAGER 20 RESEARCH


Table Aliases

Simplify queries by using table aliases.
Simplify queries by using table aliases.
SQL> SELECT emp.empno, emp.ename, emp.deptno,
2 dept.deptno, dept.loc
3 FROM emp, dept
4 WHERE emp.deptno=dept.deptno;
… can be written as ...
… can be written as ...

SQL> SELECT e.empno, e.ename, e.deptno,
2 d.deptno, d.loc
3 FROM emp e, dept d
4 WHERE e.deptno=d.deptno;


Using Table Aliases
SQL> SELECT e.empno, e.ename, e.deptno,
2 d.deptno, d.loc
3 FROM emp e, dept d
4 WHERE e.deptno=d.deptno;

EMPNO ENAME DEPTNO DEPTNO LOC
--------- ---------- --------- --------- -----------
7839 KING 10 10 NEW YORK
7698 BLAKE 30 30 CHICAGO
7782 CLARK 10 10 NEW YORK
7566 JONES 20 20 DALLAS
7654 MARTIN 30 30 CHICAGO
7499 ALLEN 30 30 CHICAGO
...

14 rows selected.


Nonequijoins
EMP SALGRADE
EMPNO ENAME SAL GRADE LOSAL HISAL
------ ------- ------ ----- ----- ------
7839 KING 5000 1 700 1200
7698 BLAKE 2850 2 1201 1400
7782 CLARK 2450 3 1401 2000
7566 JONES 2975 4 2001 3000
7654 MARTIN 1250 5 3001 9999
7499 ALLEN 1600
7844 TURNER 1500
7900 JAMES 950
... Salary in the EMP
14 rows selected. table is between
low salary and high
salary in the SALGRADE
table.


Retrieving Records
with Nonequijoins

SQL> SELECT e.ename, e.sal, s.grade
2 FROM emp e, salgrade s
3 WHERE e.sal
4 BETWEEN s.losal AND s.hisal;

ENAME SAL GRADE
---------- --------- ---------
JAMES 950 1
SMITH 800 1
ADAMS 1100 1
...
14 rows selected.


Joining More Than Two Tables
EMP DEPT
ENAME SAL DEPTNO DEPTNO DNAME
---------- --------- --------- --------- ----------
JAMES 950 30 10 ACCOUNTING
SMITH 800 20 20 RESEARCH
ADAMS 1100 20 30 SALES
MARTIN 1250 30 40 OPERATIONS
WARD 1250 30
MILLER 1300 10
… SALGRADE
14 rows selected. LOSAL HISAL GRADE
--------- --------- ---------
700 1200 1
WHERE emp.sal BETWEEN 1201 1400 2
salgrade.losal AND 1401 2000 3
salgrade.hisal 2001 3000 4
AND emp.deptno = dept.deptno 3001 9999 5


Using Multiple Joins

SQL> SELECT e.ename, e.deptno, d.dname, e.sal, s.grade
2 FROM emp e, dept d, salgrade s
3 WHERE e.deptno=d.deptno
4 AND e.sal BETWEEN s.losal and s.hisal;

ENAME DEPTNO DNAME SAL GRADE
---------- --------- -------------- --------- ---------
JAMES 30 SALES 950 1
SMITH 20 RESEARCH 800 1
ADAMS 20 RESEARCH 1100 1
MARTIN 30 SALES 1250 2
WARD 30 SALES 1250 2
MILLER 10 ACCOUNTING 1300 2
ALLEN 30 SALES 1600 3
...
14 rows selected.


Selfjoins
EMP (WORKER) EMP (MANAGER)
EMPNO ENAME MGR EMPNO ENAME
----- ------ ---- ----- --------
7839 KING
7698 BLAKE 7839 7839 KING
7782 CLARK 7839 7839 KING
7566 JONES 7839 7839 KING
7654 MARTIN 7698 7698 BLAKE
7499 ALLEN 7698 7698 BLAKE

MGR in the WORKER table is equal to EMPNO in the
MANAGER table.


Joining a Table to Itself

SQL> SELECT worker.ename||' works for '||manager.ename
2 AS WHO_WORKS_FOR_WHOM
3 FROM emp worker, emp manager
4 WHERE worker.mgr = manager.empno;

WHO_WORKS_FOR_WHOM
-------------------------------
BLAKE works for KING
CLARK works for KING
JONES works for KING
MARTIN works for BLAKE
...
13 rows selected.


Aggregating Data
by Using Group Functions


What Are Group Functions?
Group functions operate on sets of rows to give one result
Group functions operate on sets of rows to give one result
per group.
per group.
EMP
DEPTNO SAL
--------- ---------
10 2450
10 5000
10 1300
20 800
20 1100
20 3000 maximum MAX(SAL)
20 3000 salary in ---------
20 2975 the EMP table 5000
30 1600
30 2850
30 1250
30 950
30 1500
30 1250


Types of Group Functions

–
– AVG
AVG
–
– COUNT
COUNT
–
– MAX
MAX
–
– MIN
MIN
–
– SUM
SUM


Guidelines for Using Group
Functions
Many aggregate functions accept these
Many aggregate functions accept these
options:
options:
– DISTINCT
– DISTINCT
– ALL
– ALL
– NVL
– NVL


Using the AVG and SUM Functions
You can use AVG and SUM for numeric data.
You can use AVG and SUM for numeric data.

SQL> SELECT AVG(sal), SUM(sal)
2 FROM emp
3 WHERE job LIKE 'SALES%';

AVG(SAL) SUM(SAL)
-------- ---------
1400 5600


Using the MIN and MAX Functions
You can use MIN and MAX for any data type.

SQL> SELECT TO_CHAR(MIN(hiredate),'DD-MON-YYYY'),
2 TO_CHAR(MAX(hiredate),'DD-MON-YYYY')
3 FROM emp;

T0_CHAR(MIN TO_CHAR(MAX
--------- ---------
17-DEC-1980 12-JAN-1983


Using the MIN and MAX Functions

SQL> SELECT MIN(sal) AS "Lowest Salary",
2 MAX(sal) AS "Highest Salary"
3 FROM emp;

Lowest Salary Highest Salary
------------- --------------
800 5000


Using the COUNT Function
COUNT(*) returns the number of rows in a query.
COUNT(*) returns the number of rows in a query.

SQL> SELECT COUNT(*)
2 FROM emp
3 WHERE deptno = 30;

COUNT(*)
---------
6


Using the COUNT Function
COUNT(expr) returns the number of nonnull rows.
COUNT(expr) returns the number of nonnull rows.

SQL> SELECT COUNT(comm)
2 FROM emp
3 WHERE deptno = 30;

COUNT(COMM)
-----------
4


Group Functions and Null Values
Group functions ignore null values in the column.
Group functions ignore null values in the column.

SQL> SELECT AVG(comm)
2 FROM emp;

AVG(COMM)
---------
550


with Group Functions
The NVL function forces group functions to include
The NVL function forces group functions to include
null values.
null values.

SQL> SELECT AVG(NVL(comm,0))
2 FROM emp;

AVG(NVL(COMM,0))
----------------
157.14286


with Group Functions
Average commission for all people hired in 1981
Average commission for all people hired in 1981

SQL> SELECT AVG(NVL(comm,0))
2 FROM emp
3 WHERE hiredate
4 BETWEEN TO_DATE('01-JAN-1981','DD-MON-YYYY')
5 AND TO_DATE('31-DEC-1981','DD-MON-YYYY');

AVG(NVL(COMM,0))
----------------
220


Creating Groups of Data

EMP
DEPTNO SAL
--------- ---------
10 2450
10 5000 2916.6667
10 1300
20 800 average DEPTNO AVG(SAL)
20 1100 salary ------- ---------
20 3000 2175 in EMP
10 2916.6667
20 3000 table
20 2975 for each 20 2175
30 1600 department 30 1566.6667
30 2850
30 1250 1566.6667
30 950
30 1500
30 1250


Creating Groups of Data:
GROUP BY Clause
Use the GROUP BY clause to divide rows in a table
Use the GROUP BY clause to divide rows in a table
into smaller groups.
into smaller groups.

SELECT column, group_function
FROM table
[WHERE condition]
[GROUP BY group_by_expression]
[ORDER BY column];


Using the GROUP BY Clause
All columns in the SELECT list that are not in group
All columns in the SELECT list that are not in group
functions must be in the GROUP BY clause.
functions must be in the GROUP BY clause.

SQL> SELECT deptno, AVG(sal)
2 FROM emp
3 GROUP BY deptno;

DEPTNO AVG(SAL)
--------- ---------
10 2916.6667
20 2175
30 1566.6667


The GROUP BY column does not have to be in the
The GROUP BY column does not have to be in the
SELECT list.
SELECT list.

SQL> SELECT AVG(sal)
2 FROM emp
3 GROUP BY deptno;

AVG(SAL)
---------
2916.6667
2175
1566.6667


Display the number of people in each department.
Display the number of people in each department.

SQL> SELECT deptno, COUNT(*) AS "Dept Employees"
2 FROM emp
3 GROUP BY deptno;

DEPTNO Dept Employees
--------- --------------
10 3
20 5
30 6


Using a Group Function in the
ORDER BY Clause

SQL> SELECT deptno, AVG(sal)
2 FROM emp
3 GROUP BY deptno
4 ORDER BY AVG(sal);

DEPTNO AVG(SAL)
---------- ------------
30 1566.6667
20 2175
10 2916.6667


Illegal Queries
Using Group Functions

Any column or expression in the SELECT list that is
Any column or expression in the SELECT list that is
not an aggregate function must be in the GROUP BY
not an aggregate function must be in the GROUP BY
clause.
clause. usse
e
lla u
ca
Yc
BY
PB
UP
SQL> SELECT deptno, COUNT(ename)
SQL> SELECT deptno, COUNT(ename) OU
RO
2 FROM
2 FROM emp;
emp;
eG GR
tth e
h
n
in
SELECT deptno, COUNT(ename) g i
SELECT deptno, COUNT(ename) g
*
* iis
s siin
sn
ERROR at line 1: m
ERROR at line 1:
nm
n
ORA-00937: not a single-group group function
um
llu m
ORA-00937: not a single-group group function
Co
Co

Using Set Operators


The Set Operators
A B

Intersect

A B A B

Union / Union All

A B

Minus


Tables Used in This Lesson
EMP
EMPNO ENAME
EMPNO ENAME JOB
JOB MGR HIREDATE
MGR HIREDATE SAL
SAL COMM
COMM
DEPTNO
DEPTNO
--------- ---------- --------- --------- --------- ---------
--------- ---------- --------- --------- --------- --------- --------- --------
--------- --------
-
-
7839 KING
7839 KING PRESIDENT
PRESIDENT 17-NOV-81
17-NOV-81 5000
5000
10
10
7698 BLAKE
7698 BLAKE MANAGER
MANAGER 7839 01-MAY-81
7839 01-MAY-81 2850
2850
30
30
7782 CLARK
7782 CLARK MANAGER
MANAGER 7839 09-JUN-81
7839 09-JUN-81 1500
1500
10
10
7566 JONES
7566 JONES MANAGER
MANAGER 7839 02-APR-81
7839 02-APR-81 2975
2975
20
20 EMPID NAME
EMPID NAME TITLE
TITLE DATE_OUT
DATE_OUT
7654 MARTIN
7654 MARTIN SALESMAN DEPTID 7698 28-SEP-81
SALESMAN DEPTID 7698 28-SEP-81 1250
1250 1400
1400
30
30 --------- --------------------
--------- -------------------- ---------
--------- --------- --------
--------- --------
7499 ALLEN
7499 ALLEN SALESMAN -
SALESMAN - 7698 20-FEB-81
7698 20-FEB-81 1600
1600 300
300
30
30 6087 SPENCER
6087 SPENCER OPERATOR
OPERATOR 27-NOV-81
27-NOV-81
7844 TURNER
7844 TURNER SALESMAN 20
SALESMAN 20 7698 08-SEP-81
7698 08-SEP-81 1500
1500 0
0
30
30 6185 VANDYKE
6185 VANDYKE MANAGER
MANAGER 17-JAN-81
17-JAN-81
7900 JAMESEMP_HISTORY 10
7900 JAMES CLERK
CLERK 10 7698 03-DEC-81
7698 03-DEC-81 950
950
30
30 6235 BALFORD
6235 BALFORD CLERK
CLERK 22-FEB-80
22-FEB-80
7521 WARD
7521 WARD SALESMAN 20
SALESMAN 20 7698 22-FEB-81
7698 22-FEB-81 1250
1250 500
500
30
30 7788 SCOTT
7788 SCOTT ANALYST
ANALYST 05-MAY-81
05-MAY-81
7902 FORD
7902 FORD ANALYST 20
ANALYST 20 7566 03-DEC-81
7566 03-DEC-81 3000
3000
20
20 7001 JEWELL
7001 JEWELL ANALYST
ANALYST 10-JUN-81
10-JUN-81
7369 SMITH All rights reserved.
Copyright © 2004, SMITH
7369 Oracle. CLERK
CLERK 30
30 7902 17-DEC-80
7902 17-DEC-80 800
800
20
20 7499 ALLEN
7499 ALLEN SALESMAN 01-AUG-80
SALESMAN 01-AUG-80

UNION

A B


Using the UNION Operator
Display the name, employee number, and job title of
Display the name, employee number, and job title of
all employees. Display each employee only once.
all employees. Display each employee only once.

SQL> SELECT ename, empno, job
2 FROM emp
3 UNION
4 SELECT name, empid, title
5 FROM emp_history;

ENAME EMPNO JOB
---------- --------- ---------
ADAMS 7876 CLERK
ALLEN 7499 SALESMAN
BALFORD 6235 CLERK
...
20 rows selected.


Using the UNION Operator
Display the name, job title, and salary of all
Display the name, job title, and salary of all
employees.
employees.
2 FROM emp
3 UNION
4 SELECT name, title, 0
5 FROM emp_history;

ENAME JOB SAL
---------- --------- ---------
ADAMS CLERK 1100
ALLEN SALESMAN 0
ALLEN SALESMAN 1600
BALFORD CLERK 0
...
23 rows selected.


UNION ALL

A B


Using the UNION ALL Operator
Display the names, employee numbers, and job
Display the names, employee numbers, and job
titles of all employees.
titles of all employees.
2 FROM emp
3 UNION ALL
5 FROM emp_history;

ENAME EMPNO JOB
---------- --------- ---------
KING 7839 PRESIDENT
BLAKE 7698 MANAGER
CLARK 7782 MANAGER
CLARK 7782 MANAGER
...
23 rows selected.


INTERSECT

A B


Using the INTERSECT Operator

Display the distinct names, employee numbers, and
Display the distinct names, employee numbers, and
job titles of employees found in both the EMP and
job titles of employees found in both the EMP and
EMP_HISTORY tables.
EMP_HISTORY tables.
2 FROM emp
3 INTERSECT
5 FROM emp_history;

ENAME
ENAME EMPNO JOB
EMPNO JOB
---------- --------- ---------
---------- --------- ---------
ALLEN
ALLEN 7499 SALESMAN
7499 SALESMAN
CLARK
CLARK 7782 MANAGER
7782 MANAGER
SCOTT
SCOTT 7788 ANALYST
7788 ANALYST


MINUS

A B


MINUS
Display the names, employee numbers, and
Display the names, employee numbers, and
job titles for all employees who have left the
job titles for all employees who have left the
company.
company.
SQL> SELECT name, empid, title
2 FROM emp_history
3 MINUS
4 SELECT ename, empno, job
5 FROM emp;

NAME
NAME EMPID
EMPID TITLE
TITLE
---------- ---------
---------- --------- ---------
---------
BALFORD
BALFORD 6235
6235 CLERK
CLERK
BRIGGS
BRIGGS 7225
7225 PAY CLERK
PAY CLERK
...
...
6 rows selected.
6 rows selected.


SET Operator Rules
–
– The expressions in the SELECT lists must match in
The expressions in the SELECT lists must match in
number and datatype.
number and datatype.
–
– Duplicate rows are automatically eliminated except in
Duplicate rows are automatically eliminated except in
UNION ALL.
UNION ALL.
–
– Column names from the first query appear in the result.
Column names from the first query appear in the result.
–
– The output is sorted in ascending order by default
The output is sorted in ascending order by default
except in UNION ALL.
except in UNION ALL.
–
– Parentheses can be used to alter the sequence of
Parentheses can be used to alter the sequence of
execution.
execution.


Matching the SELECT
Statement

Display the department numbers,
Display the department numbers,
locations, and hiredates for all employees.
locations, and hiredates for all employees.
SQL> SELECT deptno, null location, hiredate
2 FROM emp
3 UNION
4 SELECT deptno, loc, TO_DATE(null)
5 FROM dept;


Controlling the Order of Rows
Produce an English sentence using two
Produce an English sentence using two
UNION operators.
UNION operators.
SQL>
SQL> COLUMN a_dummy NOPRINT
COLUMN a_dummy NOPRINT
SQL>
SQL> SELECT 'sing' "My dream", 3 a_dummy
SELECT 'sing' "My dream", 3 a_dummy
2
2 FROM dual
FROM dual
3
3 UNION
UNION
4
4 SELECT 'I''d like to teach', 1
SELECT 'I''d like to teach', 1
5
5 FROM dual
FROM dual
6
6 UNION
UNION
7
7 SELECT 'the world to', 2
SELECT 'the world to', 2
8
8 FROM dual
FROM dual
9
9 ORDER BY 2;
ORDER BY 2;
My dream
My dream
-------------------------
-------------------------
I'd like to teach
I'd like to teach
the world to
the world to
sing
sing


Writing Subqueries


Using a Subquery
to Solve a Problem
Who has a salary greater than Jones’s?
Who has a salary greater than Jones’s?

Main Query

? Which employees have a salary greater
than Jones’s salary?

Subquery

? What is Jones’s salary?


Subqueries

SELECT select_list
FROM table
WHERE expr operator
(SELECT select_list
FROM table);

–
– The subquery (inner query) executes once before the main
The subquery (inner query) executes once before the main
query.
query.
–
– The result of the subquery is used by the main query (outer
The result of the subquery is used by the main query (outer
query).
query).


Using a Subquery

“Who has a salary greater than Jones’?”
SQL> SELECT ename
2 FROM emp 2975
3 WHERE sal >
4 (SELECT sal
5 FROM emp
6 WHERE ename='JONES');

ENAME
----------
KING
FORD
SCOTT


Guidelines for Using Subqueries

–
– Enclose subqueries in parentheses.
Enclose subqueries in parentheses.
–
– Place subqueries on the right side of the comparison
Place subqueries on the right side of the comparison
operator.
operator.
–
– Do not add an ORDER BY clause to a subquery.
Do not add an ORDER BY clause to a subquery.
–
– Use single-row operators with single-row subqueries.
Use single-row operators with single-row subqueries.


Types of Subqueries

–
– Single-row subquery
Single-row subquery
Main query
returns
Subquery
Multiple-row subquery
CLERK
–
– Multiple-row subquery

Main query
returns CLERK
Subquery
MANAGER


Single-Row Subqueries
–
– Return only one row
Return only one row
–
– Use single-row comparison operators
Use single-row comparison operators

Operator Meaning

= Equal to

> Greater than

>= Greater than or equal to

< Less than

<= Less than or equal to

<> Not equal to


Executing Single-Row Subqueries

Who works in the same department as King?
SQL> SELECT ename, deptno
2 FROM emp 10
3 WHERE deptno =
4 (SELECT deptno
5 FROM emp
6 WHERE ename='KING');

ENAME DEPTNO
---------- ---------
KING 10
CLARK 10
MILLER 10



Who has the same manager as Blake?
2 FROM emp 7839
3 WHERE mgr =
4 (SELECT mgr
5 FROM emp
6 WHERE ename='BLAKE');

ENAME MGR
---------- ---------
BLAKE 7839
CLARK 7839
JONES 7839


Who has the same job as employee 7369 and
earns a higher salary than employee 7876?
2 FROM emp CLERK
3 WHERE job =
4 (SELECT job
5 FROM emp
6 WHERE empno = 7369)
7 AND sal > 1100
8 (SELECT sal
9 FROM emp
10 WHERE empno = 7876);

ENAME JOB
---------- ---------
MILLER CLERK


in a Subquery
Display all employees who earn the minimum salary.
2 FROM emp 800
3 WHERE sal =
4 (SELECT MIN(sal)
5 FROM emp);

ENAME JOB SAL
---------- --------- ---------
SMITH CLERK 800


What Is Wrong
with This Statement?
ry
ue
SQL> SELECT empno, ename bq
2 FROM emp su
3 WHERE sal =
ow
4 (SELECT MIN(sal)
e -r
5 FROM emp ipl
6 GROUP BY lt
deptno);
u
m
ith
ERROR: rw
to returns
ORA-01427: single-row ra
subquery more than
one row
ope
ow
no rows selected
-r
gle
S in

Will This Statement Work?

2 FROM emp
3 WHERE job =
4 (SELECT job es
lu
va
5 FROM emp
6 WHERE o
ename='SMYTHE');
n
ns
ur
no rows selected
r et
ry
ue
bq
Su


Multiple-Row Subqueries

–
– Return more than one row
Return more than one row
–
– Use the IN multiple-row comparison operator to
Use the IN multiple-row comparison operator to
compare an expression to any member in the list that a
compare an expression to any member in the list that a
subquery returns
subquery returns


in a Multiple-Row Subquery

Display all employees who earn the same salary as
the minimum salary for each department.

SQL> SELECT ename, sal, deptno
2 FROM emp 800, 950, 1300
3 WHERE sal IN
4 (SELECT MIN(sal)
5 FROM emp
6 GROUP BY deptno);

ENAME SAL DEPTNO
---------- --------- ---------
SMITH 800 20
JAMES 950 30
MILLER 1300 10


in a Multiple-Row Subquery
Display the employees who were hired on the same
date as the longest serving employee in any
department.
SQL> SELECT ename, sal, deptno,
2 TO_CHAR(hiredate,'DD-MON-YYYY')HIREDATE
3 FROM emp
4 WHERE hiredate IN
5 (SELECT MIN(hiredate)
6 FROM emp
7 GROUP BY deptno);

ENAME SAL DEPTNO HIREDATE
---------- --------- --------- -----------
SMITH 800 20 17-DEC-1980
ALLEN 1600 30 20-FEB-1981
CLARK 2450 10 09-JUN-1981


Controlling Transactions


Data Manipulation Language

–
– A DML statement is executed when you:
A DML statement is executed when you:
Add new rows to a table (INSERT)
Add new rows to a table (INSERT)
Modify existing rows in a table (UPDATE)
Modify existing rows in a table (UPDATE)
Remove existing rows from a table (DELETE)
Remove existing rows from a table (DELETE)
–
– A transaction consists of a collection of DML statements
A transaction consists of a collection of DML statements
that form a logical unit of work.
that form a logical unit of work.


Database Transactions

Database transactions can consist of:
Database transactions can consist of:
–
– DML statements that make up one consistent change to the
DML statements that make up one consistent change to the
data
data
Example: UPDATE
Example: UPDATE
–
– One DDL statement
One DDL statement
Example: CREATE
Example: CREATE
–
– One DCL statement
One DCL statement
Example: GRANT and REVOKE
Example: GRANT and REVOKE


Database Transactions

–
– Begin when the first executable SQL statement is
Begin when the first executable SQL statement is
executed
executed
–
– End with one of the following events:
End with one of the following events:
COMMIT or ROLLBACK
COMMIT or ROLLBACK
DDL or DCL statement executes (automatic commit)
DDL or DCL statement executes (automatic commit)
User exits
User exits
System crashes
System crashes


Advantages of COMMIT
and ROLLBACK

–
– COMMIT and ROLLBACK ensure data consistency.
COMMIT and ROLLBACK ensure data consistency.
–
– Users can preview data changes before making
Users can preview data changes before making
changes permanent.
changes permanent.
–
– Users can group logically related operations.
Users can group logically related operations.


Controlling Transactions
Transaction
Transaction

INSERT UPDATE INSERT DELETE

COMMIT Savepoint A Savepoint B

ROLLBACK to Savepoint B

ROLLBACK to Savepoint A

ROLLBACK


Implicit Transaction Processing
–
– An automatic commit occurs under the following
An automatic commit occurs under the following
circumstances:
circumstances:
A DDL statement is issued, such as CREATE
A DDL statement is issued, such as CREATE
A DCL statement is issued, such as GRANT
A DCL statement is issued, such as GRANT
A normal exit from SQL*Plus occurs without an explicitly
A normal exit from SQL*Plus occurs without an explicitly
issued COMMIT or ROLLBACK statement
issued COMMIT or ROLLBACK statement
–
– An automatic rollback occurs under an abnormal
An automatic rollback occurs under an abnormal
termination of SQL*Plus or a system failure.
termination of SQL*Plus or a system failure.


State of the Data Before
COMMIT or ROLLBACK
–
– The previous state of the data can be recovered.
The previous state of the data can be recovered.
–
– The current user can review the results of the DML operations
The current user can review the results of the DML operations
by using the SELECT statement.
by using the SELECT statement.
–
– Other users cannot view the results of the DML statements by
Other users cannot view the results of the DML statements by
the current user.
the current user.
–
– The affected rows are locked; other users cannot change the
The affected rows are locked; other users cannot change the
data within the affected rows.
data within the affected rows.


Committing Data

Change the department number of an employee
Change the department number of an employee
(Clark) identified by a employee number.
(Clark) identified by a employee number.
–
– Make the changes.
Make the changes.

SQL> UPDATE emp
SQL> UPDATE emp
2 SET
2 SET deptno = 10
deptno = 10
3 WHERE
3 WHERE empno = 7782;
empno = 7782;
1 row updated.
1 row updated.

• Commit the changes.
• Commit the changes.
SQL> COMMIT;
Commit complete.


State of the Data After COMMIT

• Data changes are made permanent in the
• Data changes are made permanent in the
database.
database.
• The previous state of the data is
• The previous state of the data is
permanently lost.
permanently lost.
• All users can view the results.
• All users can view the results.
• Locks on the affected rows are released;
• Locks on the affected rows are released;
those rows are available for other users to
those rows are available for other users to
manipulate.
manipulate.
• All savepoints are erased.
• All savepoints are erased.

State of the Data After ROLLBACK

Discard all pending changes by using the
Discard all pending changes by using the
ROLLBACK statement. Following a ROLLBACK:
ROLLBACK statement. Following a ROLLBACK:
–
– Data changes are undone.
Data changes are undone.
–
– The previous state of the data is restored.
The previous state of the data is restored.
–
– Locks on the affected rows are released.
Locks on the affected rows are released.

SQL> DELETE FROM employee;
14 rows deleted.
SQL> ROLLBACK;
Rollback complete.


Rolling Back Changes
to a Marker
–
– Create a marker within a current transaction by using
Create a marker within a current transaction by using
the SAVEPOINT statement.
the SAVEPOINT statement.
–
– Roll back to that marker by using the ROLLBACK TO
Roll back to that marker by using the ROLLBACK TO
SAVEPOINT statement.
SAVEPOINT statement.

SQL> UPDATE...
SQL> SAVEPOINT update_done;
Savepoint created.
SQL> INSERT...
SQL> ROLLBACK TO update_done;
Rollback complete.


Statement-Level Rollback

–
– If a single DML statement fails during execution, only
If a single DML statement fails during execution, only
that statement is rolled back.
that statement is rolled back.
–
– Oracle implements an implicit savepoint.
Oracle implements an implicit savepoint.
–
– All other changes are retained.
All other changes are retained.
–
– The user should terminate transactions explicitly by
The user should terminate transactions explicitly by
executing a COMMIT or ROLLBACK statement.
executing a COMMIT or ROLLBACK statement.


Read Consistency

–
– Read consistency guarantees a consistent view of the
Read consistency guarantees a consistent view of the
data at all times.
data at all times.
–
– Changes made by one user do not conflict with
Changes made by one user do not conflict with
changes made by another user.
changes made by another user.
–
– Read consistency ensures that on the same data:
Read consistency ensures that on the same data:
Readers do not wait for writers or other readers
Readers do not wait for writers or other readers
Writers do not wait for readers
Writers do not wait for readers


Implementation of Read Consistency

UPDATE emp Data
SET sal = 2000 blocks
WHERE ename = 'SCOTT';

Rollback
segments
User A
Changed
and
SELECT * unchanged
Read
FROM emp; data
consistent
image Before
change
“old” data
User B


Locking
The Oracle Server locks:
The Oracle Server locks:
–
– Prevent destructive interaction between concurrent
Prevent destructive interaction between concurrent
transactions
transactions
–
– Require no user action
Require no user action
–
– Automatically use the lowest level of restrictiveness
Automatically use the lowest level of restrictiveness
–
– Are held for the duration of the transaction
Are held for the duration of the transaction
–
– Have two basic modes:
Have two basic modes:
Exclusive
Exclusive
Share
Share


Locking Modes
Lock Mode Description

Exclusive lock Prevents a resource from being shared.

The first transaction to lock a resource
exclusively is the only transaction that can
alter the resource until the exclusive lock is
released.

Share Allows the resource to be shared.

Multiple users reading data can share the
data, holding share locks to prevent
concurrent access by a writer (who needs an
exclusive lock).

Several transactions can acquire share locks
on the same resource.


Implicit Locking

User Action Row-Level Lock Table-Level Lock

SELECT ... FROM table ... None None

INSERT INTO table ... X RX

UPDATE table ... X RX

DELETE FROM table ... X RX

DDL Operation None X


Explicit Locking
User Action Row-Level lock Table-Level lock

SELECT FOR UPDATE X RS [NOWAIT]

LOCK TABLE IN option None Depends on the MODE
restrictiveness used

Override the default lock mechanism:
Override the default lock mechanism:
–
– For a consistent view of data when reading across
For a consistent view of data when reading across
multiple tables
multiple tables
–
– When a transaction may change data based on other
When a transaction may change data based on other
data that must not change until the whole transaction is
data that must not change until the whole transaction is
complete
complete


Overview of PL/SQL


About PL/SQL

–
– PL/SQL is an extension to SQL with design features of
PL/SQL is an extension to SQL with design features of
programming languages.
programming languages.
–
– Data manipulation and query statements of SQL are
Data manipulation and query statements of SQL are
included within procedural units of code.
included within procedural units of code.


PL/SQL Environment

PL/SQL engine
PL/SQL Procedural
PL/SQL PL/SQL
block block SQL Statement
Executor

SQL Statement Executor

Oracle Server


Benefits of PL/SQL

Integration
Integration

Application

Shared Oracle Server
library


Benefits of PL/SQL
Improve Performance
Improve Performance

SQL
SQL
Application
Application Other DBMSs
Other DBMSs
SQL
SQL

SQL
IF...THEN
SQL Oracle with
Oracle with
Application
Application ELSE PL/SQL
SQL PL/SQL
END IF;
SQL


Benefits of PL/SQL
Modularize program development
Modularize program development

DECLARE

BEGIN

EXCEPTION

END;


Benefits of PL/SQL
–
– It is portable.
It is portable.
–
– You can declare identifiers.
You can declare identifiers.


Benefits of PL/SQL
–
– You can program with procedural language control
You can program with procedural language control
structures.
structures.
–
– It can handle errors.
It can handle errors.


Declaring Variables


PL/SQL Block Structure

•• DECLARE ––Optional
DECLARE Optional
– Variables, cursors, user-defined exceptions
– Variables, cursors, user-defined exceptions
•• BEGIN ––Mandatory
BEGIN Mandatory
– SQL statements
– SQL statements
– PL/SQL statements
– PL/SQL statements
•• EXCEPTION ––Optional
EXCEPTION Optional
– Actions to perform when
– Actions to perform when
errors occur
errors occur
•• END; ––Mandatory
END; Mandatory DECLARE

BEGIN

EXCEPTION

END;


PL/SQL Block Structure

DECLARE
DECLARE
v_variable VARCHAR2(5);
v_variable VARCHAR2(5);
BEGIN
BEGIN
SELECT
SELECT column_name
column_name
INTO
INTO v_variable
v_variable
FROM
FROM table_name;
table_name;
EXCEPTION
EXCEPTION
WHEN exception_name THEN
WHEN exception_name THEN DECLARE
...
...
END; BEGIN
END;
EXCEPTION

END;


Block Types

Anonymous Procedure Function
[DECLARE]
[DECLARE] PROCEDURE name
PROCEDURE name FUNCTION name
FUNCTION name
IS
IS RETURN datatype
RETURN datatype
IS
IS
BEGIN
BEGIN BEGIN
BEGIN BEGIN
BEGIN
--statements
--statements --statements
--statements --statements
--statements
RETURN value;
RETURN value;
[EXCEPTION]
[EXCEPTION] [EXCEPTION]
[EXCEPTION] [EXCEPTION]
[EXCEPTION]

END;
END; END;
END; END;
END;


Program Constructs

Stored
Stored
Anonymous
Anonymous procedure/
procedure/
block
block
DECLARE function
function

BEGIN Application
Application
Application
Application procedure/
procedure/
trigger
trigger function
function
EXCEPTION

Database
END; Packaged
Packaged
Database procedure/
trigger procedure/
trigger function
function


Use of Variables

Use variables for:
Use variables for:
–
– Temporary storage of data
Temporary storage of data
–
– Manipulation of stored values
Manipulation of stored values
–
– Reusability
Reusability
–
– Ease of maintenance
Ease of maintenance


Handling Variables in PL/SQL

–
– Declare and initialize variables in the declaration
Declare and initialize variables in the declaration
section.
section.
–
– Assign new values to variables in the executable
Assign new values to variables in the executable
section.
section.
–
– Pass values into PL/SQL blocks through parameters.
Pass values into PL/SQL blocks through parameters.
–
– View results through output variables.
View results through output variables.


Types of Variables

–
– PL/SQL variables:
PL/SQL variables:
Scalar
Scalar
Composite
Composite
Reference
Reference
LOB (large objects)
LOB (large objects)
–
– Non-PL/SQL variables: Bind and host variables
Non-PL/SQL variables: Bind and host variables


Types of Variables
25-OCT-99
TRUE “Four score and seven years ago
our fathers brought forth upon
this continent, a new nation,
conceived in LIBERTY, and dedicated

256120.08 to the proposition that all men
are created equal.”

Atlanta


Declaring PL/SQL Variables

Syntax
Syntax
identifier [CONSTANT] datatype [NOT NULL]
identifier [CONSTANT] datatype [NOT NULL]
[:= | DEFAULT expr];
[:= | DEFAULT expr];

Examples
Examples
Declare
Declare
v_hiredate
v_hiredate DATE;
DATE;
v_deptno
v_deptno NUMBER(2) NOT NULL := 10;
NUMBER(2) NOT NULL := 10;
v_location
v_location VARCHAR2(13) := 'Atlanta';
VARCHAR2(13) := 'Atlanta';
c_comm
c_comm CONSTANT NUMBER := 1400;
CONSTANT NUMBER := 1400;


Declaring PL/SQL Variables

Guidelines
Guidelines
–
– Follow naming conventions.
Follow naming conventions.
–
– Initialize variables designated as NOT NULL.
Initialize variables designated as NOT NULL.
–
– Initialize identifiers by using the assignment operator
Initialize identifiers by using the assignment operator
(:=) or the DEFAULT reserved word.
(:=) or the DEFAULT reserved word.
–
– Declare at most one identifier per line.
Declare at most one identifier per line.


Naming Rules
–
– Two variables can have the same name, provided they
Two variables can have the same name, provided they
are in different blocks.
are in different blocks.
–
– The variable name (identifier) should not be the same
The variable name (identifier) should not be the same
as the name of table columns used in the block.
as the name of table columns used in the block.

ffor
or
ttiion
n o
n
ven
nve s::
co n er
g c o tiiffiier s o
DECLARE ng n
miin den t mpn o
na m L iide _e mpn
DECLARE
empno NUMBER(4);
empno NUMBER(4); a na Q L
ptt a //S Q lle,, v _e
BEGIN
BEGIN do p PL S mp e v
A do PL a mp
empno A
SELECT
SELECT empno ex a
r ex
INTO
INTO empno
empno ffo r
o
FROM
FROM emp emp
WHERE
WHERE ename = 'SMITH';
ename = 'SMITH';
END;
END;


Assigning Values to Variables

Syntax
Syntax
identifier := expr;
identifier := expr;

Example
Example
• Set a predefined hiredate for new
• Set a predefined hiredate for new
employees.
employees.
v_hiredate := '31-DEC-98';
v_hiredate := '31-DEC-98';

• Set the employee name to “Maduro.”
• Set the employee name to “Maduro.”
v_ename := 'Maduro';
v_ename := 'Maduro';


Variable Initialization and Keywords
Using:
Using:
–
– Assignment operator (:=)
Assignment operator (:=)
–
– DEFAULT keyword
DEFAULT keyword
–
– NOT NULL constraint
NOT NULL constraint


Scalar Datatypes

• Hold a single value
• Hold a single value
• Have no internal components
• Have no internal components

25-OCT-99 and seven years
“Four score
ago our fathers brought
forth upon this continent, a
TRUE
new nation, conceived in

256120.08 LIBERTY, and dedicated to
the proposition that all men
are created equal.”
Atlanta

Base Scalar Datatypes
–
– VARCHAR2 (maximum_length)
VARCHAR2 (maximum_length)
–
– NUMBER [(precision, scale)]
NUMBER [(precision, scale)]
–
– DATE
DATE
–
– CHAR [(maximum_length)]
CHAR [(maximum_length)]
–
– LONG
LONG
–
– LONG RAW
LONG RAW
–
– BOOLEAN
BOOLEAN
–
– BINARY_INTEGER
BINARY_INTEGER
–
– PLS_INTEGER
PLS_INTEGER


Base Scalar Datatypes

–
– DATE
DATE
–
– TIMESTAMP
TIMESTAMP
–
– TIMESTAMP WITH TIMEZHONE
TIMESTAMP WITH TIMEZHONE
–
– TIMESTAMP WITH LOCAL TIME ZONE
TIMESTAMP WITH LOCAL TIME ZONE
–
– INTERVAL YEAR TO MONTH
INTERVAL YEAR TO MONTH
–
– INVERTAL YEAR TO SECOND
INVERTAL YEAR TO SECOND


Scalar Variable Declarations
Example
Example

v_job
v_job VARCHAR2(9);
VARCHAR2(9);
v_count
v_count BINARY_INTEGER := 0;
BINARY_INTEGER := 0;
v_total_sal
v_total_sal NUMBER(9,2) := 0;
NUMBER(9,2) := 0;
v_orderdate
v_orderdate DATE := SYSDATE + 7;
DATE := SYSDATE + 7;
c_tax_rate
c_tax_rate CONSTANT NUMBER(3,2) := 8.25;
CONSTANT NUMBER(3,2) := 8.25;
v_valid
v_valid BOOLEAN NOT NULL := TRUE;
BOOLEAN NOT NULL := TRUE;


The %TYPE Attribute

–
– Declare a variable according to:
Declare a variable according to:
A database column definition
A database column definition
Another previously declared variable
Another previously declared variable
–
– Prefix %TYPE with:
Prefix %TYPE with:
The database table and column
The database table and column
The previously declared variable name
The previously declared variable name


Declaring Variables
with the %TYPE Attribute

Example
Example

...
...
v_ename
v_ename emp.ename%TYPE;
emp.ename%TYPE;
v_balance
v_balance NUMBER(7,2);
NUMBER(7,2);
v_min_balance
v_min_balance v_balance%TYPE := 10;
v_balance%TYPE := 10;
...
...


Declaring Boolean Variables
–
– Only the values TRUE, FALSE, and NULL can be
Only the values TRUE, FALSE, and NULL can be
assigned to a Boolean variable.
assigned to a Boolean variable.
–
– The variables are connected by the logical operators
The variables are connected by the logical operators
AND, OR, and NOT.
AND, OR, and NOT.
–
– The variables always yield TRUE, FALSE, or NULL.
The variables always yield TRUE, FALSE, or NULL.
–
– Arithmetic, character, and date expressions can be
Arithmetic, character, and date expressions can be
used to return a Boolean value.
used to return a Boolean value.


Composite Datatypes

–
– PL/SQL TABLES
PL/SQL TABLES
–
– PL/SQL RECORDS
PL/SQL RECORDS


LOB Datatype Variables
Recipe
(CLOB)

Photo
(BLOB)

Movie
(BFILE)

NCLOB


Bind Variables

O/S
Bind Variable
Server


Referencing Non-PL/SQL Variables

Store the annual salary into a SQL*Plus host
Store the annual salary into a SQL*Plus host
variable.
variable.
:g_monthly_sal := v_sal / 12;
:g_monthly_sal := v_sal / 12;
–
– Reference non-PL/SQL variables as host variables.
Reference non-PL/SQL variables as host variables.
–
– Prefix the references with a colon (:).
Prefix the references with a colon (:).


DBMS_OUTPUT.PUT_LINE

–
– An Oracle-supplied packaged procedure
An Oracle-supplied packaged procedure
–
– An alternative for displaying data from a PL/SQL block
An alternative for displaying data from a PL/SQL block
–
– Must be enabled in SQL*Plus with
Must be enabled in SQL*Plus with
SET SERVEROUTPUT ON
SET SERVEROUTPUT ON


Writing Executable Statements


PL/SQL Block Syntax
and Guidelines
–
– Statements can continue over several lines.
Statements can continue over several lines.
–
– Lexical units can be separated by:
Lexical units can be separated by:
Spaces
Spaces
Delimiters
Delimiters
Identifiers
Identifiers
Literals
Literals
Comments
Comments


PL/SQL Block Syntax
and Guidelines
Identifiers
Identifiers
–
– Can contain up to 30 characters
Can contain up to 30 characters
–
– Cannot contain reserved words unless enclosed in
Cannot contain reserved words unless enclosed in
double quotation marks
double quotation marks
–
– Must begin with an alphabetic character
Must begin with an alphabetic character
–
– Should not have the same name as a database table
Should not have the same name as a database table
column name
column name


PL/SQL Block Syntax and Guidelines

Literals
Literals
–
– Character and date literals must be enclosed in single
Character and date literals must be enclosed in single
quotation marks.
quotation marks.

v_ename := 'Henderson'; values or scientific notation.
– Numbers can be simple
v_ename := 'Henderson'; values or scientific notation.
– Numbers can be simple


Commenting Code
–
– Prefix single-line comments with two dashes (--).
Prefix single-line comments with two dashes (--).
–
– Place multi-line comments between the symbols /* and
Place multi-line comments between the symbols /* and
*/.
*/.
Example
Example

...
...
v_sal NUMBER (9,2);
v_sal NUMBER (9,2);
BEGIN
BEGIN
/* Compute the annual salary based on the
/* Compute the annual salary based on the
monthly salary input from the user */
monthly salary input from the user */
v_sal := &p_monthly_sal * 12;
v_sal := &p_monthly_sal * 12;
END; -- This is the end of the transaction
END; -- This is the end of the transaction


SQL Functions in PL/SQL
–
– Available:
Available:
Single-row number
Single-row number

}
Single-row character
Single-row character
Datatype conversion
Datatype conversion
Date
Date Same as in SQL
–
– Not available:
Not available:
DECODE
DECODE
Group functions
Group functions


PL/SQL Functions

Example
Example
–
– Build the mailing list for a company.
Build the mailing list for a company.

v_mailing_address := v_name||CHR(10)||
v_mailing_address := v_name||CHR(10)||
v_address||CHR(10)||v_state||
v_address||CHR(10)||v_state||
CHR(10)||v_zip;
CHR(10)||v_zip;

–
– Convert the employee name to lowercase.
Convert the employee name to lowercase.

v_ename
v_ename := LOWER(v_ename);
:= LOWER(v_ename);


Datatype Conversion

–
– Convert data to comparable datatypes.
Convert data to comparable datatypes.
–
– Mixed datatypes can result in an error and affect
Mixed datatypes can result in an error and affect
performance.
performance.
–
– Conversion functions:
Conversion functions:
TO_CHAR
TO_CHAR
TO_DATE
TO_DATE
DECLARE
DECLARE
TO_NUMBER
TO_NUMBER
v_date
v_date VARCHAR2(15);
VARCHAR2(15);
BEGIN
BEGIN
SELECT
SELECTTO_CHAR(hiredate,
TO_CHAR(hiredate,
'MON. DD, YYYY')
'MON. DD, YYYY')
INTO
INTO v_date
v_date
FROM
FROM emp
emp
WHERE empno = 7839;
WHERE empno = 7839;
END;
END;


Datatype Conversion

This statement produces a compilation
This statement produces a compilation
error if the variable v_date is declared as
error if the variable v_date is declared as
datatype DATE.
datatype DATE.
v_date := 'January 13, 1998';
v_date := 'January 13, 1998';

To correct the error, use the TO_DATE
To correct the error, use the TO_DATE
conversion function.
conversion function.
v_date := TO_DATE ('January 13, 1998',
v_date := TO_DATE ('January 13, 1998',
'Month DD, YYYY');
'Month DD, YYYY');


Nested Blocks
and Variable Scope
–
– Statements can be nested wherever an executable
Statements can be nested wherever an executable
statement is allowed.
statement is allowed.
–
– A nested block becomes a statement.
A nested block becomes a statement.
–
– An exception section can contain nested blocks.
An exception section can contain nested blocks.
–
– The scope of an object is the region of the program that
The scope of an object is the region of the program that
can refer to the object.
can refer to the object.


Nested Blocks
and Variable Scope
An identifier is visible in the regions in which you
An identifier is visible in the regions in which you
can reference the unqualified identifier:
can reference the unqualified identifier:
–
– A block can look up to the enclosing block.
A block can look up to the enclosing block.
–
– A block cannot look down to enclosed blocks.
A block cannot look down to enclosed blocks.


Nested Blocks
and Variable Scope

Example
Example
...
...
x BINARY_INTEGER;
x BINARY_INTEGER;
BEGIN
BEGIN Scope of x
...
...
DECLARE
DECLARE
y NUMBER;
y NUMBER;
BEGIN
BEGIN Scope of y
...
...
END;
END;
...
...
END;
END;


Operators in PL/SQL

–
– Logical
Logical
–
– Arithmetic
Arithmetic
–
– Concatenation
Concatenation
–
– Parentheses to control order of
Parentheses to control order of Same as in
operations
operations SQL
–
– Exponential operator (**)
Exponential operator (**)


Operators in PL/SQL
Example
Example
–
– Increment the index for a loop.
Increment the index for a loop.
v_count
v_count := v_count + 1;
:= v_count + 1;

–
– Set the value of a Boolean flag.
Set the value of a Boolean flag.

v_equal
v_equal := (v_n1 = v_n2);
:= (v_n1 = v_n2);
– Validate an employee number if it contains a value.
– Validate an employee number if it contains a value.

v_valid
v_valid := (v_empno IS NOT NULL);
:= (v_empno IS NOT NULL);


Using Bind Variables
To reference a bind variable in PL/SQL, you must
To reference a bind variable in PL/SQL, you must
prefix its name with a colon (:).
prefix its name with a colon (:).
Example
Example

VARIABLE g_salary NUMBER
VARIABLE g_salary NUMBER
DECLARE
DECLARE
v_sal
v_sal emp.sal%TYPE;
emp.sal%TYPE;
BEGIN
BEGIN
SELECT
SELECT sal
sal
INTO
INTO v_sal
v_sal
FROM
FROM emp
emp
WHERE
WHERE empno = 7369;
empno = 7369;
:g_salary
:g_salary := v_sal;
:= v_sal;
END;
END;
/
/

Programming Guidelines

Make code maintenance easier by:
Make code maintenance easier by:
–
– Documenting code with comments
Documenting code with comments
–
– Developing a case convention for the code
Developing a case convention for the code
–
– Developing naming conventions for identifiers and
Developing naming conventions for identifiers and
other objects
other objects
–
– Enhancing readability by indenting
Enhancing readability by indenting


Code Naming Conventions

Avoid ambiguity:
Avoid ambiguity:
–
– The names of local variables and formal parameters
The names of local variables and formal parameters
take precedence over the names of database tables.
take precedence over the names of database tables.
–
– The names of columns take precedence over the
The names of columns take precedence over the
names of local variables.
names of local variables.


Indenting Code
For clarity, indent each level of code.
For clarity, indent each level of code.
Example
Example
DECLARE
DECLARE
v_deptno
v_deptno NUMBER(2);
NUMBER(2);
BEGIN
BEGIN v_location
v_location VARCHAR2(13);
VARCHAR2(13);
IF x=0 THEN
IF x=0 THEN BEGIN
BEGIN
y:=1;
y:=1; SELECT deptno,
SELECT deptno,
END IF;
END IF; loc
loc
END;
END; INTO
INTO v_deptno,
v_deptno,
v_location
v_location
FROM
FROM dept
dept
WHERE
WHERE dname = 'SALES';
dname = 'SALES';
...
...
END;
END;


Determining Variable Scope
Class Exercise
Class Exercise
...
...
DECLARE
DECLARE
V_SAL
V_SAL NUMBER(7,2) := 60000;
NUMBER(7,2) := 60000;
V_COMM
V_COMM NUMBER(7,2) := V_SAL * .20;
NUMBER(7,2) := V_SAL * .20;
V_MESSAGE
V_MESSAGE VARCHAR2(255) := ' eligible for commission';
VARCHAR2(255) := ' eligible for commission';
BEGIN ...
BEGIN ...

DECLARE
DECLARE
V_SAL
V_SAL NUMBER(7,2) := 50000;
NUMBER(7,2) := 50000;
V_COMM
V_COMM NUMBER(7,2) := 0;
NUMBER(7,2) := 0;
V_TOTAL_COMP
V_TOTAL_COMP NUMBER(7,2) := V_SAL + V_COMM;
NUMBER(7,2) := V_SAL + V_COMM;
BEGIN ...
BEGIN ...
V_MESSAGE := 'CLERK not'||V_MESSAGE;
V_MESSAGE := 'CLERK not'||V_MESSAGE;
END;
END;

V_MESSAGE := 'SALESMAN'||V_MESSAGE;
V_MESSAGE := 'SALESMAN'||V_MESSAGE;
END;
END;


Writing Control Structures


Controlling PL/SQL Flow
of Execution

You can change the logical flow of statements
You can change the logical flow of statements
using conditional IF statements and loop control
using conditional IF statements and loop control
structures.
structures.
Conditional IF
Conditional IF statements:
statements:
–
– IF-THEN-END IF
IF-THEN-END IF
–
– IF-THEN-ELSE-END IF
IF-THEN-ELSE-END IF
–
– IF-THEN-ELSIF-END IF
IF-THEN-ELSIF-END IF


IF Statements
Syntax
Syntax
IF condition THEN
IF condition THEN
statements;
statements;
[ELSIF condition THEN
[ELSIF condition THEN
statements;]
statements;]
[ELSE
[ELSE
statements;]
statements;]
END IF;
END IF;

Simple IF statement:
Simple IF statement:
Set the manager ID to 22 if the employee
Set the manager ID to 22 if the employee
name is Osborne.
name is Osborne.
IF v_ename
IF v_ename = 'OSBORNE' THEN
= 'OSBORNE' THEN
v_mgr :=
v_mgr := 22;
22;
END IF;
END IF;


Simple IF Statements

Set the job title to Salesman, the department number to 35,
Set the job title to Salesman, the department number to 35,
and the commission to 20% of the current salary if the last
and the commission to 20% of the current salary if the last
name is Miller.
name is Miller.
Example
Example

. . .
. . .
IF v_ename = 'MILLER' THEN
IF v_ename = 'MILLER' THEN
v_job := 'SALESMAN';
v_job := 'SALESMAN';
v_deptno := 35;
v_deptno := 35;
v_new_comm := sal * 0.20;
v_new_comm := sal * 0.20;
END IF;
END IF;
. . .
. . .


IF-THEN-ELSE Statement Execution
Flow

TRUE FALSE
IF condition

THEN actions
THEN actions ELSE actions
ELSE actions
(including further IFs)
(including further IFs) (including further IFs)
(including further IFs)


IF-THEN-ELSE Statements

Set a flag for orders where there are fewer than
Set a flag for orders where there are fewer than
five days between order date and ship date.
five days between order date and ship date.
Example
Example

...
...
IF v_shipdate
IF v_shipdate - v_orderdate < 5 THEN
- v_orderdate < 5 THEN
v_ship_flag
v_ship_flag := 'Acceptable';
:= 'Acceptable';
ELSE
ELSE
v_ship_flag
v_ship_flag := 'Unacceptable';
:= 'Unacceptable';
END IF;
END IF;
...
...


IF-THEN-ELSIF
Statement Execution Flow

IF condition
IF condition
TRUE FALSE

ELSIF
ELSIF
condition
condition
THEN actions
THEN actions
TRUE FALSE

ELSE
ELSE
THEN actions
THEN actions actions
actions


IF-THEN-ELSIF Statements

For a given value, calculate a percentage of that
For a given value, calculate a percentage of that
value based on a condition.
value based on a condition.
Example
Example

. . .
. . .
IF v_start > 100 THEN
IF v_start > 100 THEN
v_start := 2 * v_start;
v_start := 2 * v_start;
ELSIF v_start >= 50 THEN
ELSIF v_start >= 50 THEN
v_start := .5 * v_start;
ELSE
ELSE
END IF;
END IF;
. . .
. . .


Building Logical Conditions

–
– You can handle null values with the IS NULL operator.
You can handle null values with the IS NULL operator.
–
– Any arithmetic expression containing a null value
Any arithmetic expression containing a null value
evaluates to NULL.
evaluates to NULL.
–
– Concatenated expressions with null values treat null
Concatenated expressions with null values treat null
values as an empty string.
values as an empty string.


Logic Tables

Build a simple Boolean condition with a
Build a simple Boolean condition with a
comparison operator.
comparison operator.

AND TRUE FALSE NULL OR TRUE FALSE NULL NOT

TRUE TRUE FALSE NULL TRUE TRUE TRUE TRUE TRUE FALSE

FALSE FALSE FALSE FALSE FALSE TRUE FALSE NULL FALSE TRUE

NULL NULL FALSE NULL NULL TRUE NULL NULL NULL NULL


Boolean Conditions

What is the value of V_FLAG in each case?
What is the value of V_FLAG in each case?

v_flag := v_reorder_flag AND v_available_flag;
v_flag := v_reorder_flag AND v_available_flag;

V_REORDER_FLAG V_AVAILABLE_FLAG V_FLAG
TRUE TRUE TRUE
TRUE FALSE FALSE
NULL TRUE NULL
NULL FALSE FALSE


Iterative Control: LOOP Statements

–
– Loops repeat a statement or sequence of statements
Loops repeat a statement or sequence of statements
multiple times.
multiple times.
–
– There are three loop types:
There are three loop types:
Basic loop
Basic loop
FOR loop
FOR loop
WHILE loop
WHILE loop


Basic Loop
Syntax
Syntax
LOOP
LOOP -- delimiter
statement1;
statement1; -- statements
. . .
. . .
EXIT [WHEN condition]; -- EXIT statement
EXIT [WHEN condition];
END LOOP;
END LOOP; -- delimiter

where:
where: condition
condition is a Boolean variable or
is a Boolean variable or
expression (TRUE, FALSE,
expression (TRUE, FALSE,
or NULL);
or NULL);


Basic Loop
Example
Example

DECLARE
DECLARE
v_ordid
v_ordid item.ordid%TYPE := 601;
item.ordid%TYPE := 601;
v_counter NUMBER(2) := 1;
v_counter NUMBER(2) := 1;
BEGIN
BEGIN
LOOP
LOOP
INSERT INTO item(ordid, itemid)
VALUES(v_ordid, v_counter);
VALUES(v_ordid, v_counter);
v_counter := v_counter + 1;
v_counter := v_counter + 1;
EXIT WHEN v_counter > 10;
EXIT WHEN v_counter > 10;
END LOOP;
END LOOP;
END;
END;


FOR Loop

FOR counter in [REVERSE]
FOR counter in [REVERSE]
lower_bound..upper_bound LOOP
Syntax
Syntax
lower_bound..upper_bound LOOP
statement1;
statement1;
statement2;
statement2;
. . .
. . .
END LOOP;
END LOOP;

–
– Use a FOR loop to shortcut the test for the number of
Use a FOR loop to shortcut the test for the number of
iterations.
iterations.
–
– Do not declare the index; it is declared implicitly.
Do not declare the index; it is declared implicitly.


FOR Loop
Guidelines
Guidelines
–
– Reference the counter within the loop only; it is undefined
Reference the counter within the loop only; it is undefined
outside the loop.
outside the loop.
–
– Use an expression to reference the existing value of a
Use an expression to reference the existing value of a
counter.
counter.
–
– Do not reference the counter as the target of an
Do not reference the counter as the target of an
assignment.
assignment.


FOR Loop
Insert the first 10 new line items for order number
Insert the first 10 new line items for order number
601.
601.
Example
Example

DECLARE
DECLARE
v_ordid
v_ordid item.ordid%TYPE := 601;
item.ordid%TYPE := 601;
BEGIN
BEGIN
FOR i IN 1..10 LOOP
FOR i IN 1..10 LOOP
VALUES(v_ordid, i);
VALUES(v_ordid, i);
END LOOP;
END LOOP;
END;
END;


WHILE Loop

Syntax
Syntax
WHILE condition LOOP
WHILE condition LOOP Condition is
statement1;
statement1; evaluated at the
statement2;
statement2; beginning of
. . .
. . . each iteration.
END LOOP;
END LOOP;

Use the WHILE loop to repeat statements while a
Use the WHILE loop to repeat statements while a
condition is TRUE.
condition is TRUE.


WHILE Loop
Example
Example
ACCEPT p_new_order PROMPT 'Enter the order number:
ACCEPT p_new_order PROMPT 'Enter the order number: '
'
ACCEPT p_items -
ACCEPT p_items -
PROMPT 'Enter the number of items in this order:
PROMPT 'Enter the number of items in this order: '
'
DECLARE
DECLARE
v_count
v_count NUMBER(2) := 1;
NUMBER(2) := 1;
BEGIN
BEGIN
WHILE v_count <= &p_items LOOP
WHILE v_count <= &p_items LOOP
INSERT INTO item (ordid, itemid)
INSERT INTO item (ordid, itemid)
VALUES (&p_new_order, v_count);
VALUES (&p_new_order, v_count);
END LOOP;
END LOOP;
COMMIT;
COMMIT;
END;
END;
/
/


Nested Loops and Labels

–
– Nest loops to multiple levels.
Nest loops to multiple levels.
–
– Use labels to distinguish between blocks and loops.
Use labels to distinguish between blocks and loops.
–
– Exit the outer loop with the EXIT statement referencing
Exit the outer loop with the EXIT statement referencing
the label.
the label.


Nested Loops and Labels
...
...
BEGIN
BEGIN
<<Outer_loop>>
<<Outer_loop>>
LOOP
LOOP
v_counter := v_counter+1;
v_counter := v_counter+1;
EXIT WHEN v_counter>10;
EXIT WHEN v_counter>10;
<<Inner_loop>>
<<Inner_loop>>
LOOP
LOOP
...
...
EXIT Outer_loop WHEN total_done = 'YES';
EXIT Outer_loop WHEN total_done = 'YES';
-- Leave both loops
-- Leave both loops
EXIT WHEN inner_done = 'YES';
EXIT WHEN inner_done = 'YES';
-- Leave inner loop only
-- Leave inner loop only
...
...
END LOOP Inner_loop;
END LOOP Inner_loop;
...
...
END LOOP Outer_loop;
END LOOP Outer_loop;
END;
END;


Writing Explicit Cursors


About Cursors

Every SQL statement executed by the Oracle
Every SQL statement executed by the Oracle
Server has an individual cursor associated with it:
Server has an individual cursor associated with it:
–
– Implicit cursors: Declared for all DML and PL/SQL
Implicit cursors: Declared for all DML and PL/SQL
SELECT statements
SELECT statements
–
– Explicit cursors: Declared and named by the
Explicit cursors: Declared and named by the
programmer
programmer


Explicit Cursor Functions

Active set

7369 SMITH CLERK
7566 JONES MANAGER
Cursor 7788 SCOTT ANALYST Current row
7876 ADAMS CLERK
7902 FORD ANALYST


Controlling Explicit Cursors

No

Yes
DECLARE
DECLARE OPEN
OPEN FETCH
FETCH EMPTY? CLOSE
CLOSE

• Create a • Identify • Load the • Test for • Release
named the active current existing the active
SQL area set row into rows set
variables • Return to
FETCH if
rows
found


Controlling Explicit Cursors
Open the cursor.
Pointer

Cursor
Fetch a row from the cursor.

Pointer
Cursor
Continue until empty.

Pointer

Cursor
Close the cursor.

Cursor

Declaring the Cursor
Syntax
Syntax

CURSOR cursor_name IS
CURSOR cursor_name IS
select_statement;
select_statement;
–
– Do not include the INTO clause in the cursor declaration.
Do not include the INTO clause in the cursor declaration.
–
– If processing rows in a specific sequence is required, use the
If processing rows in a specific sequence is required, use the
ORDER BY clause in the query.
ORDER BY clause in the query.


Declaring the Cursor
Example
Example

DECLARE
DECLARE
CURSOR emp_cursor IS
SELECT empno, ename
SELECT empno, ename
FROM
FROM emp;
emp;

CURSOR dept_cursor IS
CURSOR dept_cursor IS
SELECT *
SELECT *
FROM
FROM dept
dept
WHERE deptno = 10;
WHERE deptno = 10;
BEGIN
BEGIN
...
...


Opening the Cursor
Syntax
Syntax
OPEN cursor_name;
OPEN cursor_name;
–
– Open the cursor to execute the query and identify the
Open the cursor to execute the query and identify the
active set.
active set.
–
– If the query returns no rows, no exception is raised.
If the query returns no rows, no exception is raised.
–
– Use cursor attributes to test the outcome after a fetch.
Use cursor attributes to test the outcome after a fetch.


Fetching Data from the Cursor
Syntax
Syntax
FETCH cursor_name INTO [variable1, variable2, ...]
FETCH cursor_name INTO [variable1, variable2, ...]
| record_name];
| record_name];
–
– Retrieve the current row values into output variables.
Retrieve the current row values into output variables.
–
– Include the same number of variables.
Include the same number of variables.
–
– Match each variable to correspond to the columns
Match each variable to correspond to the columns
positionally.
positionally.
–
– Test to see if the cursor contains rows.
Test to see if the cursor contains rows.


Fetching Data from the Cursor
Example
Example

FETCH emp_cursor INTO v_empno, v_ename;
FETCH emp_cursor INTO v_empno, v_ename;

...
...
OPEN defined_cursor;
OPEN defined_cursor;
LOOP
LOOP
FETCH defined_cursor INTO defined_variables
FETCH defined_cursor INTO defined_variables
EXIT WHEN ...;
EXIT WHEN ...;
...
...
-- Process the retrieved data
-- Process the retrieved data
...
...
END;
END;


Closing the Cursor

Syntax
Syntax
CLOSE
CLOSE cursor_name;
cursor_name;
–
– Close the cursor after completing the processing of the
Close the cursor after completing the processing of the
rows.
rows.
–
– Reopen the cursor, if required.
Reopen the cursor, if required.
–
– Do not attempt to fetch data from a cursor once it has
Do not attempt to fetch data from a cursor once it has
been closed.
been closed.


Explicit Cursor Attributes
Obtain status information about a cursor.
Obtain status information about a cursor.
Attribute Type Description
%ISOPEN Boolean Evaluates to TRUE if the cursor
is open
%NOTFOUND Boolean Evaluates to TRUE if the most
recent fetch does not return a row
%FOUND Boolean Evaluates to TRUE if the most
recent fetch returns a row;
complement of %NOTFOUND
%ROWCOUNT Number Evaluates to the total number of
rows returned so far


The %ISOPEN Attribute
–
– Fetch rows only when the cursor is open.
Fetch rows only when the cursor is open.
–
– Use the %ISOPEN cursor attribute before performing a
Use the %ISOPEN cursor attribute before performing a
fetch to test whether the cursor is open.
fetch to test whether the cursor is open.
Example
Example

IF NOT emp_cursor%ISOPEN THEN
IF NOT emp_cursor%ISOPEN THEN
OPEN emp_cursor;
OPEN emp_cursor;
END IF;
END IF;
LOOP
LOOP
FETCH emp_cursor...
FETCH emp_cursor...


Controlling Multiple Fetches

–
– Process several rows from an explicit cursor using a
Process several rows from an explicit cursor using a
loop.
loop.
–
– Fetch a row with each iteration.
Fetch a row with each iteration.
–
– Use the %NOTFOUND attribute to write a test for an
Use the %NOTFOUND attribute to write a test for an
unsuccessful fetch.
unsuccessful fetch.
–
– Use explicit cursor attributes to test the success of
Use explicit cursor attributes to test the success of
each fetch.
each fetch.


The %NOTFOUND
and %ROWCOUNT Attributes

–
– Use the %ROWCOUNT cursor attribute to retrieve an
Use the %ROWCOUNT cursor attribute to retrieve an
exact number of rows.
exact number of rows.
–
– Use the %NOTFOUND cursor attribute to determine
Use the %NOTFOUND cursor attribute to determine
when to exit the loop.
when to exit the loop.


Cursors and Records
Process the rows of the active set conveniently by
Process the rows of the active set conveniently by
fetching values into a PL/SQL RECORD.
fetching values into a PL/SQL RECORD.
Example
Example

DECLARE
DECLARE
SELECT empno, ename
SELECT empno, ename
FROM
FROM emp;
emp;
emp_record
emp_record emp_cursor%ROWTYPE;
emp_cursor%ROWTYPE;
BEGIN
BEGIN
OPEN emp_cursor;
OPEN emp_cursor;
LOOP
LOOP
FETCH emp_cursor INTO emp_record;
FETCH emp_cursor INTO emp_record;
...
...


Cursor FOR Loops
Syntax
Syntax

FOR record_name IN cursor_name LOOP
FOR record_name IN cursor_name LOOP
statement1;
statement1;
statement2;
statement2;
. . .
. . .
END LOOP;
– END LOOP; FOR loop is a shortcut to process explicit
– The cursor FOR loop is a shortcut to process explicit
The cursor
cursors.
cursors.
–
– Implicit open, fetch, and close occur.
Implicit open, fetch, and close occur.
–
– The record is implicitly declared.
The record is implicitly declared.


Cursor FOR Loops
Retrieve employees one by one until no more are
Retrieve employees one by one until no more are
left.
left.
Example
Example

DECLARE
DECLARE
SELECT ename, deptno
SELECT ename, deptno
FROM
FROM emp;
emp;
BEGIN
BEGIN
FOR emp_record IN emp_cursor LOOP
FOR emp_record IN emp_cursor LOOP
-- implicit open and implicit fetch occur
IF emp_record.deptno = 30 THEN
...
...
END LOOP; -- implicit close occurs
END;
END;


Cursor FOR Loops
Using Subqueries
No need to declare the cursor.
No need to declare the cursor.
Example
Example

BEGIN
BEGIN
FOR emp_record IN ( SELECT ename, deptno
FOR emp_record IN ( SELECT ename, deptno
FROM
FROM emp) LOOP
emp) LOOP
...
...
END;
END;


Advanced Explicit Cursor
Concepts


Cursors with Parameters

Syntax
CURSOR cursor_name
CURSOR cursor_name
[(parameter_name datatype, ...)]
[(parameter_name datatype, ...)]
IS
IS
select_statement;
select_statement;
– Pass parameter values to a cursor when the cursor is
opened and the query is executed.
– Open an explicit cursor several times with a different active
set each time.


Cursors with Parameters
Pass the department number and job title to the
Pass the department number and job title to the
WHERE clause.
WHERE clause.
Example
Example

DECLARE
DECLARE
CURSOR emp_cursor
CURSOR emp_cursor
(v_deptno NUMBER, v_job VARCHAR2) IS
(v_deptno NUMBER, v_job VARCHAR2) IS
SELECT
SELECT empno, ename
empno, ename
FROM
FROM emp
emp
WHERE
WHERE deptno = v_deptno
deptno = v_deptno
AND
AND job = v_job;
job = v_job;
BEGIN
BEGIN
OPEN emp_cursor(10, 'CLERK');
OPEN emp_cursor(10, 'CLERK');
...
...


The FOR UPDATE Clause

Syntax
Syntax
SELECT ...
SELECT ...
FROM
FROM ...
...
FOR UPDATE [OF column_reference][NOWAIT]
FOR UPDATE [OF column_reference][NOWAIT]
–
– Explicit locking lets you deny access for the duration of
Explicit locking lets you deny access for the duration of
a transaction.
a transaction.
–
– Lock the rows before the update or delete.
Lock the rows before the update or delete.


The FOR UPDATE Clause
Retrieve the employees who work in department 30.
Retrieve the employees who work in department 30.
Example
Example

DECLARE
DECLARE
SELECT empno, ename, sal
SELECT empno, ename, sal
FROM
FROM emp
emp
WHERE deptno = 30
WHERE deptno = 30
FOR UPDATE NOWAIT;
FOR UPDATE NOWAIT;


The WHERE CURRENT OF Clause

Syntax
WHERE CURRENT OF cursor
WHERE CURRENT OF cursor
– Use cursors to update or delete the current row.
– Include the FOR UPDATE clause in the cursor query to
lock the rows first.
– Use the WHERE CURRENT OF clause to reference
the current row from an explicit cursor.


The WHERE CURRENT OF Clause
Example
Example
DECLARE
DECLARE
CURSOR sal_cursor IS
CURSOR sal_cursor IS
SELECT
SELECT sal
sal
FROM
FROM emp
emp
WHERE
WHERE deptno = 30
deptno = 30
FOR UPDATE NOWAIT;
FOR UPDATE NOWAIT;
BEGIN
BEGIN
FOR emp_record IN sal_cursor LOOP
FOR emp_record IN sal_cursor LOOP
UPDATE
UPDATE emp
emp
SET
SET sal = emp_record.sal * 1.10
sal = emp_record.sal * 1.10
WHERE CURRENT OF sal_cursor;
WHERE CURRENT OF sal_cursor;
END LOOP;
END LOOP;
COMMIT;
COMMIT;
END;
END;


Cursors with Subqueries

Example
Example
DECLARE
DECLARE
CURSOR my_cursor IS
CURSOR my_cursor IS
SELECT t1.deptno, dname, STAFF
SELECT t1.deptno, dname, STAFF
FROM
FROM dept t1, (SELECT deptno,
dept t1, (SELECT deptno,
count(*) STAFF
count(*) STAFF
FROM
FROM emp
emp
GROUP BY deptno) t2
GROUP BY deptno) t2
WHERE t1.deptno = t2.deptno
WHERE t1.deptno = t2.deptno
AND
AND STAFF >= 5;
STAFF >= 5;


Handling Exceptions


Handling Exceptions with PL/SQL
–
– What is an exception?
What is an exception?
Identifier in PL/SQL that is raised during execution
Identifier in PL/SQL that is raised during execution
–
– How is it raised?
How is it raised?
An Oracle error occurs.
An Oracle error occurs.
You raise it explicitly.
You raise it explicitly.
–
– How do you handle it?
How do you handle it?
Trap it with a handler.
Trap it with a handler.
Propagate it to the calling environment.
Propagate it to the calling environment.


Handling Exceptions

Trap the exception Propagate the exception
DECLARE DECLARE

BEGIN BEGIN
Exception Exception
is raised is raised
EXCEPTION EXCEPTION

Exception Exception is
is trapped END; END; not trapped

Exception
propagates to calling
environment


Exception Types

–
– Predefined Oracle Server
Predefined Oracle Server
–
–
–
–
Non-predefined Oracle Server
Non-predefined Oracle Server
User-defined
User-defined
} Implicitly
raised

Explicitly raised


Trapping Exceptions
Syntax
Syntax
EXCEPTION
EXCEPTION
WHEN exception1 [OR exception2 . . .] THEN
WHEN exception1 [OR exception2 . . .] THEN
statement1;
statement1;
statement2;
statement2;
. . .
. . .
[WHEN exception3 [OR exception4 . . .] THEN
[WHEN exception3 [OR exception4 . . .] THEN
statement1;
statement1;
statement2;
statement2;
. . .]
. . .]
[WHEN OTHERS THEN
[WHEN OTHERS THEN
statement1;
statement1;
statement2;
statement2;
. . .]
. . .]


Trapping Exceptions Guidelines

–
– WHEN OTHERS is the last clause.
WHEN OTHERS is the last clause.
–
– EXCEPTION keyword starts exception-handling
EXCEPTION keyword starts exception-handling
section.
section.
–
– Several exception handlers are allowed.
Several exception handlers are allowed.
–
– Only one handler is processed before leaving the
Only one handler is processed before leaving the
block.
block.


Trapping Predefined
Oracle Server Errors

–
– Reference the standard name in the exception-
Reference the standard name in the exception-
handling routine.
handling routine.
–
– Sample predefined exceptions:
Sample predefined exceptions:
NO_DATA_FOUND
NO_DATA_FOUND
TOO_MANY_ROWS
TOO_MANY_ROWS
INVALID_CURSOR
INVALID_CURSOR
ZERO_DIVIDE
ZERO_DIVIDE
DUP_VAL_ON_INDEX
DUP_VAL_ON_INDEX


Predefined Exception
Syntax
Syntax
BEGIN SELECT ... COMMIT;
EXCEPTION
WHEN NO_DATA_FOUND THEN
statement1;
statement2;
WHEN TOO_MANY_ROWS THEN
statement1;
WHEN OTHERS THEN
statement1;
statement2;
statement3;
END;


Trapping Non-Predefined Oracle
Server Errors

Declare Associate Reference

Declarative section Exception-handling
section

• Name the • Code the PRAGMA • Handle the
exception EXCEPTION_INIT raised
exception


Non-Predefined Error
Trap for Oracle Server error number
Trap for Oracle Server error number
–2292, an integrity constraint violation.
–2292, an integrity constraint violation.
DECLARE
DECLARE
e_emps_remaining EXCEPTION;
EXCEPTION;
e_emps_remaining EXCEPTION;
e_emps_remaining 1
PRAGMA EXCEPTION_INIT (
e_emps_remaining, -2292);
e_emps_remaining, -2292);
e_emps_remaining, -2292); 2
v_deptno
v_deptno dept.deptno%TYPE := &p_deptno;
dept.deptno%TYPE := &p_deptno;
BEGIN
BEGIN
DELETE FROM dept
DELETE FROM dept
WHERE
WHERE deptno = v_deptno;
deptno = v_deptno;
COMMIT;
COMMIT;
EXCEPTION
EXCEPTION
WHEN e_emps_remaining THEN
WHEN e_emps_remaining THEN 3
DBMS_OUTPUT.PUT_LINE ('Cannot remove dept ' ||
DBMS_OUTPUT.PUT_LINE ('Cannot remove dept ' ||
TO_CHAR(v_deptno) || '. Employees exist. ');
TO_CHAR(v_deptno) || '. Employees exist. ');
END;
END;


Trapping User-Defined Exceptions

Declare Raise Reference

Declarative Executable Exception-handling
section section section

• Name the • Explicitly raise • Handle the
exception the exception by raised
using the RAISE exception
statement


User-Defined Exception
Example
Example
DECLARE
DECLARE
EXCEPTION;
e_invalid_product EXCEPTION;
e_invalid_product EXCEPTION; 1
BEGIN
BEGIN
UPDATE
UPDATE product
product
SET
SET descrip = '&product_description'
descrip = '&product_description'
WHERE
WHERE prodid = &product_number;
prodid = &product_number;
IF SQL%NOTFOUND THEN
IF SQL%NOTFOUND THEN
RAISE e_invalid_product;
RAISE e_invalid_product; 2
END IF;
END IF;
COMMIT;
COMMIT;
EXCEPTION
EXCEPTION
e_invalid_product
WHEN e_invalid_product THEN
WHEN e_invalid_product THEN 3
DBMS_OUTPUT.PUT_LINE('Invalid product number.');
DBMS_OUTPUT.PUT_LINE('Invalid product number.');
END;
END;


Functions for Trapping Exceptions

–
– SQLCODE
SQLCODE
Returns the numeric value for the error code
Returns the numeric value for the error code
–
– SQLERRM
SQLERRM
Returns the message associated with the error number
Returns the message associated with the error number


Functions for Trapping Exceptions
Example
Example
DECLARE
v_error_code NUMBER;
v_error_message VARCHAR2(255);
BEGIN
...
EXCEPTION
...
WHEN OTHERS THEN
ROLLBACK;
v_error_code := SQLCODE ;
v_error_message := SQLERRM ;
INSERT INTO errors VALUES(v_error_code,
v_error_message);
END;


Calling Environments
SQL*Plus Displays error number and message
to screen
Procedure Displays error number and message
Builder
to screen
Accesses error number and message
Oracle in a trigger by means of the
Developer ERROR_CODE and ERROR_TEXT
Forms packaged functions
Precompiler Accesses exception number through
application the SQLCA data structure

An enclosing Traps exception in exception-
PL/SQL block handling routine of enclosing block

RAISE_APPLICATION_ERROR
Procedure
Syntax
Syntax
raise_application_error (error_number,
raise_application_error (error_number,
message[, {TRUE | FALSE}]);
message[, {TRUE | FALSE}]);

–
– A procedure that lets you issue user-defined error
A procedure that lets you issue user-defined error
messages from stored subprograms
messages from stored subprograms
–
– Called only from an executing stored subprogram
Called only from an executing stored subprogram


RAISE_APPLICATION_ERROR
Procedure
–
– Used in two different places:
Used in two different places:
Executable section
Executable section
Exception section
Exception section
–
– Returns error conditions to the user in a manner
Returns error conditions to the user in a manner
consistent with other Oracle Server errors
consistent with other Oracle Server errors


Procedure and Function


Package


Trigger


Managing Dependencies


Q U E S T I O N S
A N S W E R S


Oracle sql & plsql

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