Understand data control (GRANT, REVOKE) and transaction control (COMMIT, ROLLBACK).
Beyond defining and manipulating data, SQL provides commands for managing access and ensuring data integrity during operations. These are handled by Data Control Language (DCL) and Transaction Control Language (TCL). DCL is concerned with security and user permissions. The two main DCL commands are `GRANT` and `REVOKE`. `GRANT` is used by database administrators to give specific permissions to users. For example, a DBA can grant a user the ability to `SELECT` data from a specific table but not to `UPDATE` or `DELETE` it. This allows for fine-grained control over data access. `REVOKE` is the opposite; it removes previously granted permissions from a user. TCL deals with managing transactions. A transaction is a sequence of operations performed as a single logical unit of work. All operations in a transaction must succeed; if any part fails, the entire transaction is rolled back. The `COMMIT` command is used to save all the changes made during the current transaction, making them permanent. The `ROLLBACK` command is used to undo all the changes made in the current transaction, restoring the database to the state it was in before the transaction began. A third command, `SAVEPOINT`, can be used to set an intermediate point within a transaction to which you can later roll back. TCL is essential for maintaining the ACID properties of a database, especially consistency and durability.