Using single row functions to customize output

Using Single-Row
Functions to
Customize Output

SQL Functions
Function
Input
arg 1
arg 2
arg n
Function performs
action
Output
Result
value

Two Types of SQL Functions
Single-row
functions
Multiple-row
functions
Return one result
per row
Return one result
per set of rows
Functions

Single-Row Functions
• Single-row functions:
• Manipulate data items
• Accept arguments and return one value
• Act on each row that is returned
• Return one result per row
• May modify the data type
• Can be nested
• Accept arguments that can be a column or an expression
function_name [(arg1, arg2,...)]

Single-Row Functions
Conversion
Character
Number
Date
General
Single-row
functions

Character Functions
Character
functions
LOWER
UPPER
INITCAP
CONCAT
SUBSTR
LENGTH
INSTR
LPAD | RPAD
TRIM
REPLACE
Case-manipulation
functions
Character-manipulation
functions

Case-Manipulation Functions
• These functions convert case for character strings:
Function Result
LOWER('SQL Course') sql course
UPPER('SQL Course') SQL COURSE
INITCAP('SQL Course') Sql Course

SELECT employee_id, last_name, department_id
FROM employees
WHERE LOWER(last_name) = 'higgins';
Using Case-Manipulation Functions
• Display the employee number, name, and department number for
employee Higgins:
SELECT employee_id, last_name, department_id
FROM employees
WHERE last_name = 'higgins';
no rows selected

Character-Manipulation Functions
• These functions manipulate character strings:
Function Result
CONCAT('Hello', 'World') HelloWorld
SUBSTR('HelloWorld',1,5) Hello
LENGTH('HelloWorld') 10
INSTR('HelloWorld', 'W') 6
LPAD(salary,10,'*') *****24000
RPAD(salary, 10, '*') 24000*****
REPLACE
('JACK and JUE','J','BL')
BLACK and BLUE
TRIM('H' FROM 'HelloWorld') elloWorld

SELECT employee_id, CONCAT(first_name, last_name) NAME,
job_id, LENGTH (last_name),
INSTR(last_name, 'a') "Contains 'a'?"
FROM employees
WHERE SUBSTR(job_id, 4) = 'REP';
Using the Character-Manipulation
Functions
2
31 2
1
3

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

SELECT ROUND(45.923,2), ROUND(45.923,0),
ROUND(45.923,-1)
FROM DUAL;
Using the ROUND Function
DUAL is a dummy table that you can use to view results
from functions and calculations.
3
31 2
1 2

Using the TRUNC Function
SELECT ROUND(45.923,2), ROUND(45.923),
ROUND(45.923,-1)
FROM DUAL;
3
31 2
1 2

SELECT last_name, salary, MOD(salary, 5000)
FROM employees
WHERE job_id = 'SA_REP';
Using the MOD Function
• For all employees with job title of Sales Representative, calculate
the remainder of the salary after it is divided by 5,000.

SELECT last_name, hire_date
FROM employees
WHERE hire_date < ''01-FEB-88';';
Working with Dates
• The Oracle database stores dates in an internal numeric format:
century, year, month, day, hours, minutes, and seconds.
• The default date display format is DD-MON-RR.
• Enables you to store 21st-century dates in the
20th century by specifying only the last two digits of the year
• Enables you to store 20th-century dates in the
21st century in the same way

Working with Dates
• SYSDATE is a function that returns:
• Date
• Time

Arithmetic with Dates
• Add or subtract a number to or from a date for a resultant date value.
• Subtract two dates to find the number of days between those dates.
• Add hours to a date by dividing the number of hours by 24.

SELECT last_name, (SYSDATE-hire_date)/7 AS WEEKS
FROM employees
WHERE department_id = 90;
Using Arithmetic Operators
with Dates

Date Functions
Function Result
MONTHS_BETWEEN Number of months between two dates
ADD_MONTHS Add calendar months to date
NEXT_DAY Next day of the date specified
LAST_DAY Last day of the month
ROUND Round date
TRUNC Truncate date

Using Date Functions
Function Result
MONTHS_BETWEEN
('01-SEP-95','11-JAN-94')
19.6774194
ADD_MONTHS ('11-JAN-94',6) '11-JUL-94'
NEXT_DAY ('01-SEP-95','FRIDAY') '08-SEP-95'
LAST_DAY ('01-FEB-95') '28-FEB-95'

Using Date Functions
Assume SYSDATE = '25-JUL-03':
Function Result
ROUND(SYSDATE,'MONTH') 01-AUG-03
ROUND(SYSDATE ,'YEAR') 01-JAN-04
TRUNC(SYSDATE ,'MONTH') 01-JUL-03
TRUNC(SYSDATE ,'YEAR') 01-JAN-03

Practice 3: Overview of Part 1
• This practice covers the following topics:
• Writing a query that displays the current date
• Creating queries that require the use of numeric, character, and date
functions
• Performing calculations of years and months of service for an employee

Conversion Functions
Implicit data type
conversion
Explicit data type
conversion
Data type
conversion

Implicit Data Type Conversion
• For assignments, the Oracle server can automatically convert
the following:
From To
VARCHAR2 or CHAR NUMBER
VARCHAR2 or CHAR DATE
NUMBER VARCHAR2
DATE VARCHAR2

Implicit Data Type Conversion
• For expression evaluation, the Oracle Server can automatically
convert the following:
From To
VARCHAR2 or CHAR NUMBER
VARCHAR2 or CHAR DATE

Explicit Data Type Conversion
NUMBER CHARACTER
TO_CHAR
TO_NUMBER
DATE
TO_CHAR
TO_DATE

Using the TO_CHAR Function with Dates
•
• The format model:
• Must be enclosed by single quotation marks
• Is case-sensitive
• Can include any valid date format element
• Has an fm element to remove padded blanks or suppress leading zeros
• Is separated from the date value by a comma
TO_CHAR(date, 'format_model')

Elements of the Date Format Model
Element Result
YYYY Full year in numbers
YEAR Year spelled out (in English)
MM Two-digit value for month
MONTH Full name of the month
MON Three-letter abbreviation of the month
DY Three-letter abbreviation of the day of the
week
DAY Full name of the day of the week
DD Numeric day of the month

Elements of the Date Format Model
• Time elements format the time portion of the date:
• Add character strings by enclosing them in double quotation marks:
• Number suffixes spell out numbers:
DD "of" MONTH 12 of OCTOBER
ddspth fourteenth
HH24:MI:SS AM 15:45:32 PM

SELECT last_name,
TO_CHAR(hire_date, 'fmDD Month YYYY')
AS HIREDATE
FROM employees;
Using the TO_CHAR Function with Dates
…

Using the TO_CHAR Function with
Numbers
• These are some of the format elements that you can use with
the TO_CHAR function to display a number value as a
character:
Element Result
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
, Prints a comma as thousands indicator
TO_CHAR(number, 'format_model')

SELECT TO_CHAR(salary, '$99,999.00') SALARY
FROM employees
WHERE last_name = 'Ernst';
Using the TO_CHAR Function with
Numbers

Using the TO_NUMBER and TO_DATE
Functions
• Convert a character string to a number format using the TO_NUMBER
function:
• Convert a character string to a date format using the TO_DATE
function:
• These functions have an fx modifier. This modifier specifies the exact
matching for the character argument and date format model of a
TO_DATE function.
TO_NUMBER(char[, 'format_model'])
TO_DATE(char[, 'format_model'])

RR Date Format
Current Year
1995
1995
2001
2001
Specified Date
27-OCT-95
27-OCT-17
27-OCT-17
27-OCT-95
RR Format
1995
2017
2017
1995
YY Format
1995
1917
2017
2095
If two digits
of the
current
year are:
0–49
0–49 50–99
50–99
The return date is in
the current century
The return date is
in the century after
the current one
the century before
the current one
the current century
If the specified two-digit year is:

Example of RR Date Format
• To find employees hired prior to 1990, use the RR date format,
which produces the same results whether the command is run
in 1999 or now:
SELECT last_name, TO_CHAR(hire_date, 'DD-Mon-YYYY')
FROM employees
WHERE hire_date < TO_DATE('01-Jan-90','DD-Mon-RR');

Nesting Functions
• Single-row functions can be nested to any level.
• Nested functions are evaluated from deepest level to the least deep
level.
F3(F2(F1(col,arg1),arg2),arg3)
Step 1 = Result 1
Step 2 = Result 2
Step 3 = Result 3

SELECT last_name,
UPPER(CONCAT(SUBSTR (LAST_NAME, 1, 8), '_US'))
FROM employees
Nesting Functions

General Functions
• The following functions work with any data type and pertain to
using nulls:
• NVL (expr1, expr2)
• NVL2 (expr1, expr2, expr3)
• NULLIF (expr1, expr2)
• COALESCE (expr1, expr2, ..., exprn)

NVL Function
• Converts a null value to an actual value:
• Data types that can be used are date, character, and number.
• Data types must match:
• NVL(commission_pct,0)
• NVL(hire_date,'01-JAN-97')
• NVL(job_id,'No Job Yet')

SELECT last_name, salary, NVL(commission_pct, 0),
(salary*12) + (salary*12*NVL(commission_pct, 0)) AN_SAL
FROM employees;
Using the NVL Function
…
1
1 2
2

SELECT last_name, salary, commission_pct,
NVL2(commission_pct,
'SAL+COMM', 'SAL') income
FROM employees WHERE department_id IN (50, 80);
Using the NVL2 Function
1 2
2
1

SELECT first_name, LENGTH(first_name) "expr1",
last_name, LENGTH(last_name) "expr2",
NULLIF(LENGTH(first_name), LENGTH(last_name)) result
FROM employees;
Using the NULLIF Function
…
1
2
3
1 2 3

Using the COALESCE Function
• The advantage of the COALESCE function over the NVL function is
that the COALESCE function can take multiple alternate values.
• If the first expression is not null, the COALESCE function returns that
expression; otherwise, it does a COALESCE of the remaining
expressions.

SELECT last_name,
COALESCE(manager_id,commission_pct, -1) comm
FROM employees
ORDER BY commission_pct;
Using the COALESCE Function
…

Conditional Expressions
• Provide the use of IF-THEN-ELSE logic within a SQL statement
• Use two methods:
• CASE expression
• DECODE function

CASE Expression
• Facilitates conditional inquiries by doing the work of an IF-THEN-
ELSE statement:
CASE expr WHEN comparison_expr1 THEN return_expr1
[WHEN comparison_expr2 THEN return_expr2
WHEN comparison_exprn THEN return_exprn
ELSE else_expr]
END

SELECT last_name, job_id, salary,
CASE job_id WHEN 'IT_PROG' THEN 1.10*salary
WHEN 'ST_CLERK' THEN 1.15*salary
WHEN 'SA_REP' THEN 1.20*salary
ELSE salary END "REVISED_SALARY"
FROM employees;
Using the CASE Expression
• Facilitates conditional inquiries by doing the work of an IF-THEN-
ELSE statement:
…
…

DECODE Function
• Facilitates conditional inquiries by doing the work of a CASE
expression or an IF-THEN-ELSE statement:
DECODE(col|expression, search1, result1
[, search2, result2,...,]
[, default])

SELECT last_name, job_id, salary,
DECODE(job_id, 'IT_PROG', 1.10*salary,
'ST_CLERK', 1.15*salary,
'SA_REP', 1.20*salary,
salary)
REVISED_SALARY
FROM employees;
Using the DECODE Function
…
…

SELECT last_name, salary,
DECODE (TRUNC(salary/2000, 0),
0, 0.00,
1, 0.09,
2, 0.20,
3, 0.30,
4, 0.40,
5, 0.42,
6, 0.44,
0.45) TAX_RATE
FROM employees
Using the DECODE Function
• Display the applicable tax rate for each employee in department
80:

Using single row functions to customize output

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