SQL implements Discretionary Access Controls (DAC) through the use of GRANT and REVOKE statements

SQL implements Discretionary Access Controls (DAC) through the use of GRANT and REVOKE statements. DAC is an access control model where a resource owner (or a designated administrator) can grant or deny access to other users at their own discretion.

• GRANT: This statement is used to give specific permissions to a user or a role. These permissions can include the ability to select, insert, update, or delete data from a table, execute a stored procedure, or create objects.

  • Example 1: Granting SELECT and UPDATE permissions on a table to a specific user.

    SQL

    GRANT SELECT, UPDATE ON Employees TO 'user1'@'localhost';
    

  • Example 2: Granting all permissions on a database to a user.

    SQL

    GRANT ALL PRIVILEGES ON corporate_database.* TO 'admin_user'@'localhost';
    

  • Example 3: Granting permissions to a role, which can then be assigned to multiple users.

    SQL

    GRANT SELECT ON Orders TO AnalystRole;
    

• REVOKE: This statement is used to remove permissions that were previously granted. It is the direct opposite of the GRANT statement.

  • Example 1: Revoking UPDATE permission from a user.

    SQL

    REVOKE UPDATE ON Employees FROM 'user1'@'localhost';
    

  • Example 2: Revoking all privileges from a user on a database.

    SQL

    REVOKE ALL PRIVILEGES ON corporate_database.* FROM 'admin_user'@'localhost';
    

Why Other Options Are Incorrect

• A. INSERT and DELETE: These are Data Manipulation Language (DML) commands used to add or remove data from a table. They are operations on the data itself, not commands for managing access permissions.

• C. PUBLIC and PRIVATE: While these keywords can appear in some database systems, they are not the primary commands for implementing DAC. They may be used in specific contexts (e.g., in Oracle, PUBLIC refers to all users), but they are not the core mechanism.

• D. ROLLBACK and TERMINATE: ROLLBACK is a Transaction Control Language (TCL) command used to undo changes made in a transaction. TERMINATE is not a standard SQL command; similar functionality is often handled by a command like KILL or CANCEL, but it's used to end a process, not manage access control.