Database Programming using SQL

Introduction to Database
Lab: Introduction to Oracle and SQL
(CSE 3151)
Lab - 0
Ajit K Nayak, Ph.D.
Siksha ‘O’ Anusandhan University
Aug 2016

Ajit K Nayak1.2Introduction to databases
Relational Model
 The relational model uses a set of tables/
relations to represent data and the relationship
among those data for a specific enterprise.
 Each table is arranged in a two dimensional
matrix, i.e. columns and rows.
 Each column has a unique name called
fields/attributes of the relation.
 Each row is a record of the relation type.

Example: Table / relation

SQL
 Edgar F. Codd, designed a set of rules
(Codds rule) for ideal relational database
management system.
 Structured Query Language (SQL) was one of
the first commercial languages that is used
widely as a database language.
 SQL adheres to some of the Codd’s rules.
 SQL became a standard of ANSI in 1986, and
of the International Organization for
Standardization (ISO) in 1987.
 Both the standards are identical

Oracle
 Oracle Database is an object-relational
database management system developed
by Oracle Corporation.
 It uses SQL as the language and complies to
the ANSI/ISO standards
 SQL consists of
 a data definition language(DDL),
 a data manipulation language(DML),
 a and Data Control Language(DCL).
 The names are according to their function.

DDL
 A data definition language or data
description language (DDL) provides syntax
for defining data structures, especially
database schemas.
 Statements are
 CREATE : to create tables etc.
 DROP: to delete table
 ALTER: to change an object (field, type, etc)
 RENAME: to rename a table

DML
 A data manipulation language (DML)
provides a family of syntax elements used to
operate on the data in table.
 Statements are
 SELECT : to retrieve data from table.
 INSERT: to insert records into the table
 UPDATE: to change data inside table
 DELETE: to delete rows/records from a table

DCL
 A data control language (DCL) is used to
control access to data stored in a database
(Authorization).
 Statements are
 GRANT : to allow specified users to perform
specified tasks.
 REVOKE: to cancel previously granted or denied
permissions.

Datatypes - Minimal
Data type Description
CHARACTER(n) Character string. Fixed-length n
VARCHAR(n) Character string. Variable length. Maximum
length n
BOOLEAN Stores TRUE or FALSE values
INTEGER Integer numerical (no decimal).
NUMERIC(p,s) precision p, scale s. Example: numeric(5,2) is
a number that has 3 digits before the decimal
and 2 digits after the decimal
DATE Stores year, month, and day values
TIME Stores hour, minute, and second values

Experiment Time
Let’s create, insert and retrieve

Create Table - I
 SQL is case insensitive. However, try to follow
one case only.
 To create a table we need atleast:
 The table name (r)
 the names of the columns (A1, A2, . . .)
 Datatype of columns in order (D1, D2, D3, . . .)
 Syntax
create table r (A1 D1, A2 D2, ..., An Dn);

Create Table - II
 Let’s create the table as shown.
 create table instructor (
ID char(5),
name varchar(20),
dept_name varchar(20),
salary numeric(8,2));
instructor

Insert Records - I
 To insert into a table we need:
 The table name (r)
 value of the columns in order (V1, V2, V3, . . .)
 Syntax
insert into r values(V1, V2, ..., Vn);

Insert records - II
 Let’s insert records in the table instructor.
 insert into instructor values (‘10101’, ’Srinivasan’,
’Comp.Sci’, 65000);
 insert into instructor values (‘12121’, ’Wu’,
’Finance’, 90000);
 . . .
instructor

Retrieve data – The SELECT statement
 The select statement lists the attribute values in
the result of a query
 Syntax
select column(s)
from table(s)
where condition(s) (optional)
 NOTE: SQL names are case insensitive (i.e., you
may use upper- or lower-case letters.)
 E.g., Name ≡ NAME ≡ name

The SELECT statement -II
 from and where are two clauses used with select
statements. The where clause is optional
 Example
select name
from instructor
Output : Lists all the names inserted into table
instructor.
Srinivasan
Wu
Mozart
Einstein
. . .

The SELECT statement -III
 Example
select name
from instructor
where salary < 65000
Output
Lists all the names in table instructor
having salary less than 65000.
Mozart
El Said
. . .

Assignment - I

End of Lab 1
Thank You

Lab: Basic Operations in SQL
(CSE 3151)
Lab - 2
Ajit K Nayak, Ph.D.
Aug 2016

Review
 SQL is a standard for database (relational)
programming having following components
 DDL
 To define the relations
 DML
 To access or manipulate data inside relation
 DCL
 To provide access permissions
 TCL (Transaction Control Language)
 Transaction control (COMMIT, ROLLBACK,
SAVEPOINT)

Transaction Control - I
 Transaction is a unit of a program execution
that accesses and possibly modifies various
data objects (reading, writing)
 Some of the transaction make permanent
changes in the database but some are not.
 COMMIT is used to save changes permanently
in a database manually.
 DDL commands uses implicit COMMIT (auto
commit),
 But DML needs explicit COMMIT. (to be issued
manually)

Transaction Control - II
 Until you commit a transaction (DML):
 You can see any changes you have made during
the transaction by querying the modified tables.
(local change)
 But other users cannot see the changes.
 After you commit the transaction, the changes are
visible to other users' statements that execute after
the commit. (global change)
 You can roll back (undo) any changes made
during the transaction with the ROLLBACK
statement.
 So, before leaving the lab issue: COMMIT;

UPDATE
 Used to change/modify one or more records.
 Conditional Update
UPDATE instructor
SET name = „Uthhapa‟
WHERE name = „Wu‟;
 Update all rows
UPDATE instructor
SET name = salary = salary+100;

DELETE
 To delete one or more rows
 Conditional delete
DELETE FROM instructor
WHERE name = „Wu‟;
 Delete all rows
DELETE FROM instructor;

The Select Statement - I
 The select statement may be used in following
situations
 Projection: to choose one or
more columns in a table.
 Selection: to choose one or
more columns in a table.

The Select Statement - II
 Joining: to bring together data that is
stored in different tables by creating a
link between them.

Operations
 Arithmetic Operations
 +, -, *, /
 Column Alias
 Concatenation Operator (II)
 DISTINCT operator
 Comparison Operations (<, >, >=,<=, BETWEEN,
IN, LIKE, NULL)
 Logical Operators (AND, OR, NOT)

Examples - I
 Arithmetic
1) SELECT name, salary, salary * 0.3
FROM instructor;
 Alias
2) SELECT name, salary, salary *0.3 AS diff
FROM instructor;
 Concatenation (||)
3) SELECT name || „ belongs to ‟||
dept_name “Employee Dept”
FROM instructor;

Examples - II
SELECT dept_name from instructor;
 Displays all the departments with duplcates
 DISTINCT : Eliminates duplicate rows
4) SELECT DISTINCT dept_name
FROM instructor;
 BETWEEN (Between two values inclusive)
5) SELECT name, salary
FROM instructor
WHERE salary BETWEEN 40000 AND 60000;

Examples - III
 IN (set): to chose values from a list
6) SELECT name, dept_name
FROM instructor
WHERE dept_name IN (Comp.Sci, Physics);
 LIKE: wildcard search
 % : denotes zero or more characters
 _ : denotes one character
7) SELECT name
FROM employees
WHERE name LIKE ‟E%‟;

Examples - IV
 AND
8) SELECT id, name
FROM instructor
WHERE salary >= 50000
AND dept_name LIKE ‟Comp%‟;
 NOT
9) SELECT name, id
FROM employees
WHERE dept_name
NOT IN (‟History‟, ‟Biology‟);

Group Functions
 group functions operate on sets of rows to give
one result per group.
 These sets may be the whole table or the table
split into groups.
 AVG
 COUNT
 MAX
 MIN
 STDDEV
 SUM
 VARIANCE

Group Functions Example
SELECT AVG(salary), MAX(salary),
MIN(salary), SUM(salary)
FROM instructor;

Group Functions Example
1) SELECT AVG(salary), MAX(salary),
MIN(salary), SUM(salary)
FROM instructor;
Who is getting highest salary?
2) SELECT name, Dept, salary
FROM instructor
WHERE salary = (
SELECT MAX(salary)
FROM instructor);

Maintaining Lab Records
 Use plain A4 sheet
 Design a cover page stating
 Reg. No, Name, Branch, Section, session, college
name, university name
 Design a content page containing assignment
number, date, page no of solution
 Write the question, query, output of the query
 Submit for verification in next lab.

Task
 Execute all the queries discussed
 Solve Assignment 2

End of Lab 2
Thank You

Lab: Functions in SQL
(CSE 3151)
Lab - 3
Ajit K Nayak, Ph.D.
Aug 2016

Dual Table
 If you want to have some task without using a
table…
 Today’s date
 Solve an arithmetic expression (3+4)
 . . .
 But the select command needs a table…
 Oracle provides a 1x1 dummy table for these purpose
 SELECT sysdate from DUAL;
 SELECT 3+4 from DUAL;
 SELECT * from DUAL;
 SELECT 1 from DUAL;

Single row functions: character
 To manipulate character data
 LOWER, UPPER, INITCAP, CONCAT, SUBSTR, INSTR, LENGTH,
LPAD, RPAD, TRIM, REPLACE
 Examples
 LOWER(’SQL Course’) output: sql course
 UPPER(’SQL Course’) output: SQL COURSE
 INITCAP(’SQL Course’) output: Sql Course
 CONCAT(’Hello’, ’World’) output: HelloWorld
 SUBSTR(’HelloWorld’,1,5) output: Hello
 LENGTH(’HelloWorld’) output: 10
 INSTR(’HelloWorld’, ’W’) output: 6
 LPAD(salary,10,’*’) output: *****24000
 RPAD(salary, 10, ’*’) output: 24000*****
 TRIM(’H’ FROM ’HelloWorld’) output: elloWorld

Single row functions: Numeric
 To Manipulate Numeric data
 ROUND, TRUNC, MOD, ABS, ACOS, ASIN, ATAN,
ATAN2, BITAND, CEIL, COS, COSH, EXP, FLOOR, LN,
LOG , POWER, SIGN, SIN, SINH, SQRT, TAN,
TANH, TRUNC
 Examples
 ROUND(45.926, 2) output: ?
 TRUNC(45.926, 2) output: ?
 MOD(1600, 300) output: ?
 ABS(-87) output: ?
 CIEL(3.456) output: ?
 COS(60) output: ?
 POWER(2,3) output: ?

End of Lab 3
Thank You

Lab: Sorting and DDL
(CSE 3151)
Lab - 4
Ajit K Nayak, Ph.D.
Aug 2016

Sorting rows
 The clause ORDER BY is used to display sorted
outputs.
 It has to be used as the last clause of any
select statement.
SELECT name, salary
FROM instructor
ORDER BY salary ASC;
 ASC is default case.
 DESC is used for descending order
 It is also possible to sort according to multiple columns

Grouping rows
 The clause can’t be used to select individual
rows. Used with group functions.
 The result is sorted ASC by default
 Order by clause may e used with this clause.
SELECT dept_name, AVG(salary)
FROM instructor
GROUP BY dept_name;
 Do not used WHERE, HAVING clause may be
used to restrict resultant groups.
HAVING AVG(salary) > 60000;

DDL Commands - I
 ALTER TABLE statement can be used to:
 ADD a new column
 MODIFY an existing column
 Define a default value for the new column
 DROP a column

ALTER TABLE - I
 ADD a column to an existing table
ALTER TABLE instructor
ADD (doj date);
 Adds a new column doj at the end.
 MODIFY a column datatype
MODIFY (name varchar2(30));
 Can modify type, size, default values of cols.

ALTER TABLE - II
 MODIFY a default value
MODIFY (salary numeric(8,2) default 1000);
 DROP a column
DROP COLUMN doj;
 MARK UNUSED a column
SET UNUSED (doj);
At a later time
DROP UNUSED COLUMNS;

DDL - II
 Renaming objects
 Rename a table
RENAME instructor TO faculty;
 Rename a table column
RENAME COLUMN dept_name TO department;

DDL - III
 Truncate statement removes all the rows
from a table.
TRUNCATE TABLE instructor;
 Drop statement removes rows and table
structure
DROP TABLE instructor;

End of Lab 4
Thank You

Lab: Data Constraints
(CSE 3151)
Lab - 5
Ajit K Nayak, Ph.D.
Aug 2016

Ajit K Nayak5.2Introduction to databases LAB
Constraints in Oracle
 Constraints enforce rules into the tables that
 Can enforce rules on data when a row is inserted,
updated, or deleted. That is the constraints must be
satisfied for the operation to succeed.
 Prevent the deletion of a table if there are
dependencies from other table
 Constraints can be defined in either column
level or table level
 Either a constraint can be defined while creating a
table (CREATE TABLE), Or it can be added at a later
time to an existing table (ALTER TABLE)

Constraint Types
Constraints
I/O
Constraints
Business rule
Constraints
Primary Key
Constraint
Foreign Key
Constraint
Not NULL
Constraint
Unique
Constraint
CHECK
Constraint

Constraints - I
Constraints Description
NOT NULL Specifies that the column can’t contain a null
value
UNIQUE Specifies a column or combination of columns
whose values must be unique for all rows in the
table but allows some values to be null.
PRIMARY KEY Uniquely identifies each row of the table
(unique + not null)
FOREIGN KEY Requires values in one table to match values in
another table.
CHECK Requires a value in the database to comply
with a specified condition.

Constraint Levels
 Column level Constraints
 Applied to the current column called inline
specification.
 i.e. local to a specific column
 Can’t be applied if data constraints span across
multiple columns in a table
 Table level Constraints
 It is applied when data constraints span across
multiple columns in a table (out-of-line specification)
 Defined after defining all table columns
 Stored as a part of global table definition

NULL Value
 NULL value
 Used for a column when we do not have a value
for that column
 It can be used for columns of any data type
 When no value is supplied for a column, Oracle
assumes NULL value for that column (default)
 It is different from blank or zero values
 If the column has already a NULL value in it, then
Oracle ignores the UNIQUE, FOREIGN, and CHECK
constraints
 NOT NULL constraints must be declared inline. All
other constraints can be declared either inline or
out of line.

NOT NULL
 If the table is not yet created
CREATE TABLE customers(
id INT NOT NULL,
name VARCHAR2(20) NOT NULL,
address VARCHAR2(25) ,
salary NUMERIC(18, 2) );
 If the table is existing
ALTER TABLE CUSTOMERS
MODIFY salary NUMERIC(18, 2) NOT NULL;

UNIQUE - I in-line
id INT NOT NULL,
name VARCHAR2(20) UNIQUE,
address VARCHAR2(25) ,
salary NUMERIC(18, 2) );
 Out-of-line
. . .
UNIQUE (name, address) );
OR
CONSTRAINT cust_add UNIQUE(name, address)
A Name may be assigned
to the constraint

UNIQUE - II
 In Existing table
ALTER TABLE customers
ADD UNIQUE (address);
 In Existing table (with constraint name)
ADD CONSTRAINT cust_add UNIQUE(name, address);
 Drop a constraint
DROP CONSTRAINT cust_add;

Primary Key
 CREATE TABLE
id INT PRIMARY KEY,
. . .
Or
PRIMARY KEY (id, name)
Or
CONSTRAINT cust_id PRIMARY KEY (id, name)
 ALTER TABLE
ADD PRIMARY KEY (id, name)
 DROP KEY
DROP CONSTRAINT cust_id

Foreign Key - I
 A FOREIGN KEY in one table points to a PRIMARY KEY in
another table.
cid LastName FirstName Address City
1 Hansen Ola Timoteivn 10 Sandnes
2 Svendson Tove Borgvn 23 Sandnes
3 Pettersen Kari Storgt 20 Stavanger
oid OrderNo cid
1 77895 3
2 44678 3
3 22456 2
4 24562 1
“cid" column in the orders table points
to the “cid" column in the customer
table.
The “cid" column is the PRIMARY KEY
in the customer table and is a
FOREIGN KEY in the order table.

Foreign Key – Create table
 Column level
CREATE TABLE orders(
oid int PRIMARY KEY,
OrderNo int NOT NULL,
cid int REFERENCES customer(cid));
 Table level
cid int,
CONSTRAINT fk_order FOREIGN KEY (cid)
REFERENCES customer(cid));

Foreign Key – Alter table
 Column level
ALTER TABLE orders
ADD FOREIGN KEY (cid)
REFERENCES customer(cid);
 Table level
ALTER TABLE orders
ADD CONSTRAINT fk_order
FOREIGN KEY (cid)
REFERENCES customer(cid);
 DROP
ALTER TABLE orders
DROP CONSTRAINT fk_order;

After Referencing
 Extract information from two tables with
referential integrity
SELECT lastname, address, city, orderNo
FROM customer, orders
WHERE customer.cid = order.cid;

Restrictions with referential integrity
 Deletion restriction
 Rows containing Referenced key values in the
parent table can’t be deleted that have
dependent rows in the child table.
 Method 1 (Manual/ not advised)
 Delete the row from child table
 Then delete from parent table
 Method 2 (Automated)
 Use either ON DELETE CASCADE
 or ON DELETE SET NULL clauses
 Then oracle will automatically delete corresponding
rows in child table along with rows of parent table

Restrictions with referential integrity
 Insertion restriction
 A row can’t be inserted into the child table if
referenced key values are not available in the
parent table.
 Method
 Insert into the parent table
 Then insert into child table

Deleting rows with referential integrity
 Example:
cid int,
CONSTRAINT fk_order FOREIGN KEY (cid)
REFERENCES customer(cid)
ON DELETE CASCADE
);

CHECK constraint
 Applying business rule (mob# and email id)
CREATE TABLE customer (
. . .
mobNo char(10),
eMail varchar2(50));
ALTER TABLE customer
ADD CONSTRAINT ch_mob
CHECK (mobNo LIKE
'[0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9]');
ALTER TABLE customer
ADD CONSTRAINT ch_mail
CHECK (eMail Like '_%@_%._%');

End of Lab 5
Thank You

Lab: Subquery
(CSE 3151)
Lab - 6
Ajit K Nayak, Ph.D.
Aug 2016

Subquery?
 Some times you may need two queries to
solve a single problem.
 Ex: Who has a salary greater than Abel’s?
 Subquery: What is Abel’s Salary?
 Mainquery: Which employees salaries greater than
Abel’s salary.
 Syntax:
SELECT <columns>
FROM <table>
WHERE <expression>
(SELECT <columns>
FROM <table>
WHERE <expression>);
Subquery/
Innerquery
Mainquery/
Outerquery

Example
 Ex: Find the employee names getting more
salary than Abel’s.
SELECT name
FROM employee
WHERE salary >
(SELECT salary
FROM employees
WHERE name = “Abel”);

Subquery Types
 Single-row subqueries: Queries that return only
one row from the inner SELECT statement
 Use single-row comparison operators
 =, >, >=, <, <=, <>
 Multiple-row subqueries: Queries that return
more than one row from the inner SELECT
statement
 Use multiple-row comparison operators
 IN, ANY, ALL

Single-row subqueries - I
 Display the employees name and job ID
whose job ID is the same as that of employee
141.
SELECT name, job_id
FROM employees
WHERE job_id =
(SELECT job_id
FROM employees
WHERE employee_id = 141);

Single-row subqueries - II
 Display the employees name and job_id whose job ID
is the same as that of employee 141 and salary same
as that of employee 143.
SELECT name, job_id
FROM employees
WHERE job_id =
(SELECT job_id
FROM employees
WHERE employee_id = 141)
AND salary >
(SELECT salary
FROM employees
WHERE employee_id = 143);

Single-row subqueries - III
 Display the employees name, job_id, salary, who are
getting min salary.
SELECT name, job_id, salary
FROM employees
WHERE salary =
(SELECT MIN(salary)
FROM employees);
 List the departments getting min salary greater than the dept 50
SELECT dept_id, MIN(salary)
FROM employees
GROUP BY dept_id
HAVING MIN(salary) >
(SELECT MIN(salary)
FROM employees
WHERE dept_id = 50);

Multiple-row subqueries - I
 List the employees of different department getting
minimum salary.
SELECT name, salary, dept_id
FROM employees
WHERE salary IN
(SELECT MIN(salary)
FROM employees
GROUP BY dept_id);

Multiple-row subqueries - II
 Find employees info of employees getting salary less
than any IT programmers
SELECT emp_id, name, job_id, salary
FROM employees
WHERE salary < ANY
(SELECT salary
FROM employees
WHERE job_id = ’IT_PROG’)
AND job_id <> ’IT_PROG’;

Multiple-row subqueries - III
 Find employees info of employees salary less than all IT
programmers
SELECT employee_id, last_name, job_id, salary
FROM employees
WHERE salary < ALL
(SELECT salary
FROM employees
WHERE job_id = ’IT_PROG’)
AND job_id <> ’IT_PROG’;

Problem with Subquery
 A common problem with subqueries is
no rows being returned by the inner
query.

End of Lab 6
Thank You

Lab: Joining Tables
(CSE 3151)
Lab - 7
Ajit K Nayak, Ph.D.
Aug 2016

Joining Tables
 to obtain data from more than one table using
equality and non-equality joins
 Join a table to itself by using a self join

Obtaining data from multiple tables

Cartesian Products
 A Cartesian product is formed when:
 A join condition is omitted
 A join condition is invalid
 All rows in the first table are joined to all rows in the
second table
 A Cartesian product tends to generate a large
number of rows, and the result is rarely useful.
 To avoid a Cartesian product, always include
a valid join condition in a WHERE clause.

Cartesian Products: Example
 SELECT last_name, department_name dept_name
FROM employees, departments;

Generating a Cartesian Product

Joining Tables: Equijoins
 SELECT table1.column, table2.column
FROM table1, table2
WHERE table1.column1 = table2.column2;
 SELECT employees.employee_id, employees.last_name,
employees.department_id, departments.department_id,
departments.location_id
FROM employees, departments
WHERE employees.department_id =
departments.department_id;

Additional Search Conditions
 SELECT last_name, employees.department_id,
department_name
FROM employees, departments
WHERE employees.department_id =
departments.department_id
AND last_name = ’Matos’;

Using Table alias
 SELECT e.employee_id, e.last_name, e.department_id,
d.department_id, d.location_id
FROM employees e , departments d
WHERE e.department_id = d.department_id;

Joining More than Two Tables
 SELECT e.last_name, d.department_name, l.city
FROM employees e, departments d, locations l
WHERE e.department_id = d.department_id
AND d.location_id = l.location_id;

Joining more than two tables

Self Joins
 Sometimes you need to join a table to itself.
 Ex: To find the name of each employee’s manager,
 Need to join the EMPLOYEES table to itself, or
perform a self join.
 SELECT worker.last_name || ’ works for ’||
manager.last_name
FROM employees worker, employees manager
WHERE worker.manager_id = manager.employee_id

Self Joins

End of Lab 7
Thank You

Database Programming using SQL

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