Structured Query Language (SQL) is used to define, manipulate, and retrieve data from a relational database. The main SQL commands are: Data Definition Language (DDL) to define schemas; Data Manipulation Language (DML) to add, modify and delete data; Data Control Language (DCL) to grant and revoke user privileges; Transaction Control Language (TCL) to commit and rollback transactions; and Data Query Language (DQL) to fetch data with SELECT statements. Common DDL commands are CREATE, ALTER, and DROP to create, modify, and remove tables. DML includes INSERT, UPDATE, and DELETE to add, modify and remove rows.

2. Introduction to SQL:-
•Structured query language (SQL) is a
programming language for storing and
processing information in a relational database.
•-> A relational database stores information in
tabular form, with rows and columns
representing different data attributes and the
various relationships between the data values..

3. VARIOUS TYPES OF SQL COMMANDS:-
1.Data Definition Language(DDL)
2.Data Manipulation Language(DML)
3.Data Control Language(DCL)
4.Transaction Control Language(TCL)
5.Data Query Language(DCL)

4. FLOW CHART:

5. Data Definition Language:-
• DDL (Data Definition Language) is a type of SQL command used
to define data structures and modify data. These commands
are used to create or modify the tables in SQL.
• DDL COMMANDS:
1.Create
2.Alter
3.Truncate
4.Drop
5.Rename

6. 1.CREATE COMMAND:-
This command is used to create a new table in SQL. The
user has to give information like table name, column
names, and their datatypes.
SYNTAX:
CREATE TABLE table-name
(column1 data-type(size),
column2 data-type(size),
………………
column N data-type(size));
Ex: create table student( sno number(3),
sname varchar2(10),
saddress varchar2(10));

7. 2. ALTER COMMAND:-
• To change the structure of a table. This change could
be either modify an existing attribute or add a new
attribute.
• SYNTAX:
ALTER TABLE table-name {ADD / MODIFY} (column1
datatype1);
• Ex1: alter table stu add (sname varchar2(15));
• Ex2: alter table stu modify(sname char(6));

8. 3.TRUNCATE COMMAND:-
To remove all rows from a table we can use ‘truncate’
command.
•SYNTAX: TRUNCATE TABLE <tablename>
Ex: TRUNCATE table stu;
4.DROP COMMAND:-
The drop command can be used to drop a table.
SYNTAX: DROP TABLE table_name;
Ex: drop table stu;

9. 5.RENAME COMMAND:-
Rename command can be used to change the
name of an exiting table.
SYNTAX: RENAME <old name> to <new name>;
Ex: rename stu to student;

10. DATA MANIPULATION LANGUAGE:-
• A data manipulation language (DML) is a computer
programming language used for adding , deleting, and
modifying data in a database.
• DML COMMANDS:
• 1.Insert
• 2.Update
• 3.Delete
• 4.Merge

11. INSERT COMMAND:-
The insert command is used to add rows to a table .
SYNTAX: insert into <tablename> values(a list of data values):
Ex: insert into student values (101, ‘brahmam’, ‘gnt’);
2.UPDATE COMMAND:-
An update statement changes the data of one or more records in a
table.
SYNTAX: update table_name SET column1 = value1, column2 =
value2,… WHERE condition;
Ex: UPDATE customers SET contact name = ‘Vishnu’, city = ‘viz’
WHERE customer id =1;

12. DELETE COMMAND:-
• The delete statement is used to remove one or more
records from a table.
• SYNTAX:
DELETE FROM table_name WHERE condition;
• Ex:
delete from customer where customer name = ‘Vishnu’;

13. DATA CONTROL LANGUAGE (DCL):-
• DCL commands are used to enforce database security in a
multiple user database environment.
• Only Database Administrator’s or owners of the database
object can provide /remove privileges on a database object.
• Two types of DCL commands. They are,
GRANT COMMAND
 REVOKE COMMAND

14. GRANT COMMAND:-
• GRANT is a command used to provide access or privileges on
the database objects to the users.
• SYNTAX: grant privileges on <object name> to <user name>;
Ex:GRANT SELECT, UPDATE ON MY_TABLE TO SOME_USER, ANOTHER_USER
;
•  REVOKE COMMAND:- The REVOKE command user access
rights or privileges to the database objects.
• SYNTAX: revoke privileges on <object name> from <user
name>;
• Ex: REVOKE SELECT, UPDATE ON MY_TABLE FROM USER1, USER2;

15. TRANSACTION CONTROL LANGUAGE(TCL):-
• Transaction changes can be made permanent to a database
only if they are committed. A transaction executable
statements and end explicitly with their rollback or commit
statement and implicity.
Commit
Rollback
Save point

16. CON…
• COMMIT:- Commit command is used to save all the
transactions to the database.
• SYNTAX: COMMIT;
• Rollback:- Rollback command is used to undo transactions
that have not already been saved to the database.
• SYNTAX: ROLLBACK;
• Ex: delete from customers where age =25;
• ROLLBACK;
• SAVEPOINT:- It is used to roll the transaction back to a
certain point without rolling back the entire transaction.
• SYNTAX: SAVEPOINT savepoint_name;

17. DATA QUERY LANGUAGE(DQL):-DQL is used to
fetch the data from the database
• It uses only one command i.e, SELECT
• SELECT: This is the same as the projection operation of
relational algebra. It is used to select the attribute based
on the condition described by WHERE clause.
1.SYNTAX:SELECT expressions
2.FROM TABLES
3.WHERE conditions;
Ex: SELECT emp_name
FROM employee
WHERE age > 20;