IMCA - Introduction to RDBMS

DCL – Data Control Language

These commands are used to manage user permissions and access in the database.

**GRANT** | Gives users access privileges to database objects (like tables, views, etc.)
**REVOKE** | Removes previously granted privileges from users

Example:

GRANT SELECT ON Employees TO User1;
REVOKE INSERT ON Employees FROM User1;

TCL – Transaction Control Language

These commands are used to **manage transactions** (i.e., groups of SQL operations treated as a single unit) in the database.

**COMMIT** | Saves the changes made in a transaction permanently to the database
**ROLLBACK** | Undoes the changes made in a transaction (reverts to the last committed state)
**SAVEPOINT** | Sets a point in a transaction that you can roll back to later without rolling back the entire transaction
**SET TRANSACTION** | Sets properties for a transaction, like isolation level or read/write mode

Example:

BEGIN; -- or START TRANSACTION;

DELETE FROM Employees WHERE ID = 101;
UPDATE Accounts SET Balance = Balance - 5000 WHERE AccID = 201;

COMMIT; -- saves both actions

-- OR

ROLLBACK; -- cancels both actions