Transactions & ACID

Atomicity is all-or-nothing, Consistency keeps rules valid, Isolation keeps concurrent transactions from interfering, Durability survives crashes – and isolation levels tune the Isolation strictness.

A transaction makes many statements all-or-nothing; autocommit finalises each statement alone, so wrap multi-step work in an explicit BEGIN/COMMIT.

A savepoint is a bookmark inside a transaction; ROLLBACK TO it undoes only the work after the bookmark, so one bad step does not sink the whole transaction.

ACID guarantees all-or-nothing correctness for money, BASE trades instant consistency for availability and scale where brief staleness is acceptable.