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Data Control Language (DCL) command
It is used to control users’ rights in accessing data in the database. It uses two
controls, GRANT and REVOKE.

(a) GRANT
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It is used to give users access privileges to a database. The syntax is GRANT privilege Chapter Eight: Databases and Database Management Systems
[, privilege], ON privilege_ level TO account_name; For example, If you need to
give user_M access to the database student, the query will be:
GRANT ALL ON
student
TO user_M;

(b) REVOKE
It is used to revoke access permissions that were previously granted to prevent a user
from accessing the database objects. The syntax is REVOKE privilege_name ON
object_name FROM {user_name |PUBLIC |role_name}

For example: If you need to remove user_M from accessing the database student,
the query will be:

REVOKE ALL
ON student
FROM user_M;

Transaction Control Language (TCL) command
Transaction Control Language command is used to handle database transactions.
It keeps track of the modifications made by the data manipulation language. It also
enables the grouping of statements into logical transactions. The transaction control
language consists of COMMIT, ROLLBACK, and SAVEPOINT.

(a) COMMIT
COMMIT command is used to save any transaction into the database permanently.
When we use any DML command like INSERT, UPDATE or DELETE, the changes
made by these commands are not permanent; until the current session is closed, the
changes made by these commands can be rolled back. To avoid that, we use the
COMMIT command to mark the changes as permanent. The syntax is COMMIT;
Example:
Delete from student_registration
Where address = 250 Dodoma;

Commit;

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Student’s Book Form Five

Computer Science Form 5.indd 475 23/07/2024 12:35