SQL TCL — Transaction Control Language | Learn Computer Academy

TCL — Transaction Control Language

TCL statements manage groups of changes as a single unit, called a transaction — so a set of related changes either all happen, or none do. This is the last of the four SQL command families.

COMMIT

Saves all changes made in the current transaction permanently.

COMMIT;

Makes every change since the last COMMIT permanent.
Cannot be undone once committed.

Common Mistake

Forgetting to COMMIT and losing changes when the session ends.

ROLLBACK

Cancels all uncommitted changes in the current transaction.

ROLLBACK;

Cancels any changes made since the last COMMIT.
Returns the database to its previous, safe state.

Common Mistake

Assuming ROLLBACK can undo changes that were already committed — it can't.

SAVEPOINT

Marks a point inside a transaction that you can roll back to, without undoing everything.

SAVEPOINT savepoint_name;

SAVEPOINT BeforeUpdate;

Creates a named restore point inside the current transaction.
A later ROLLBACK TO can return to this point instead of the very start.

Common Mistake

Relying on SAVEPOINT across separate sessions — it only lives within one transaction.

With all four SQL families covered — DDL, DML, DCL, and TCL — the next set of lessons moves into querying: filtering, sorting, and grouping the data you now know how to define, change, control, and commit.