Wednesday, April 13, 2016

What is – DML, DDL, DCL,TCL and DQL





What is DDL Command  : (Data Definition Language)

It is used to create and modify the structure of database objects in database.

Command
Description
CREATE
Creates a new table, a view of a table, or other object in database
ALTER
Modifies an existing database object, such as a table
DROP
Deletes an entire table, a view of a table or other object in the database



What is DML Command  : (Data Manipulation Language)

It is used to retrieve, store, modify, delete, insert and update data in database.

Command
Description
INSERT
Creates a record
UPDATE
Modifies records
DELETE
Deletes records


What is DCL Command  : (Data Control Language)

It is used to create roles, permissions, and referential integrity as well it is used to control access to database by securing it.

Command
Description
GRANT
Gives a privilege to user
REVOKE
Takes back privileges granted from user


What is DQL Command  : (Data Query Language)

It is used to fetch the records from Physical files


Command
Description
SELECT
Retrieves certain records from one or more tables

What is TCL Command  : (Transaction Control Language)

It is used to manage different transactions occurring within a database.

Command
Description
COMMIT
To commit the bunch of SQL Statements
ROLLBACK 
To revert a transaction