SQL Data Control Language (DCL)

Introduction to DCL

• DCL stands for Data Control Language.
• DCL is used to control user access in a database.
• This command is related to the security issues.
• Using DCL command, it allows or restricts the user from accessing data in database schema.
DCL commands are as follows,
1. GRANT
2. REVOKE

• It is used to grant or revoke access permissions from any database user.

1. GRANT COMMAND

• GRANT command gives user's access privileges to the database.
• This command allows specified users to perform specific tasks.

Syntax:
GRANT <privilege list>
ON <relation name or view name>
TO <user/role list>;


In the above example, user 'ABC' has been given permission to view and modify the records in the 'employee' table.

2. REVOKE COMMAND

• REVOKE command is used to cancel previously granted or denied permissions.
• This command withdraw access privileges given with the GRANT command.
• It takes back permissions from user.

Syntax:
REVOKE <privilege list>
ON <relation name or view name>
FROM <user name>;

Difference between GRANT and REVOKE command.

GRANT	REVOKE
GRANT command allows a user to perform certain activities on the database.	REVOKE command disallows a user to perform certain activities.
It grants access privileges for database objects to other users.	It revokes access privileges for database objects previously granted to other users.
Example: GRANT privilege_name ON object_name TO {      user_name|PUBLIC|role_name } [WITH GRANT OPTION];	Example: REVOKE privilege_name ON object_name FROM {      user_name|PUBLIC|role_name }