Summary - Locking

Update a balance safely with SELECT FOR UPDATE.

A lock controls concurrent access. FOR UPDATE locks a row; deadlock is mutual waiting.

SELECT * FROM accounts WHERE id = 1 FOR UPDATE;

Summary locking query.

All columns are selected from accounts. WHERE keeps only the rows where id = 1 FOR UPDATE holds.

Exercise Summary - Locking

Summary: lock the id=1 row in accounts with FOR UPDATE.

Show example solution

SELECT * FROM accounts WHERE id = 1 FOR UPDATE;