DCL

📘 What is DCL (Data Control Language)?

DCL (Data Control Language) is a subset of SQL used to control access to data in a database.
If SQL were a building, DCL would be the security system — determining who gets in, what they can do, and whether they can touch anything sensitive.

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🧩 Role of DCL in SQL:

SQL is divided into several sub-languages:

Type	Purpose	Examples
DDL	Define structure	CREATE, ALTER
DML	Manage data	SELECT, INSERT, UPDATE, DELETE
DCL	Control access	GRANT, REVOKE
TCL	Manage transactions	COMMIT, ROLLBACK

So, DCL = security & permissions layer of SQL.

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🔐 Key DCL Commands:

1. GRANT

Gives a user specific privileges on a database object.

GRANT SELECT, INSERT ON customers TO gaurav;

Gives user gaurav permission to SELECT and INSERT into the customers table.

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2. REVOKE

Removes previously granted permissions.

REVOKE INSERT ON customers FROM gaurav;

Takes away the INSERT permission from gaurav on the customers table.

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🛡️ Why DCL Matters:

Scenario	DCL Usage Example
Limit access for junior devs	Only allow SELECT, not DELETE
Secure sensitive tables	HR salary table → only HR team gets access
Handle third-party integrations	Grant limited access to APIs or analytics tools

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⚠️ DCL is not transactional (usually)

• In most DBMS systems, GRANT and REVOKE are immediate and auto-committed.

• That means you can’t rollback a GRANT if it goes wrong.

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🧠 Interview Line:

“DCL is the part of SQL that handles permissions using GRANT and REVOKE to control who can access or modify database objects.”