Guided Notes

Transactions

BEGIN, COMMIT, ROLLBACK, and keeping data consistent with ACID.

All or nothing

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A transaction groups several changes into one all-or-nothing unit.

Transferring 100 from Ada to Grace takes two updates: subtract from Ada, add to Grace. If the system crashed between them, 100 would simply vanish.

Inside a transaction, both updates happen or neither does β€” the database is never left half-updated.