Sql Transactions — Free Sql Tutorial

TL;DR: Learn Sql Transactions in Sql with a free, beginner-friendly tutorial, examples and practice for Indian students on Syllab.in.

Sql Transactions in Sql

A transaction is a sequence of SQL operations that must ALL succeed or ALL fail together. If any step fails, the entire transaction is rolled back — the database returns to its previous state.

ACID properties: Atomicity (all or nothing), Consistency (data remains valid), Isolation (concurrent transactions don't interfere), Durability (committed data survives crashes).

Transaction commands: BEGIN (start), COMMIT (save all changes), ROLLBACK (undo all changes since BEGIN). SAVEPOINT creates a checkpoint within a transaction.

Real-world example: bank transfer — debit account A and credit account B must BOTH succeed. If the credit fails after the debit, we ROLLBACK to prevent money disappearing.

BEGIN;  -- or START TRANSACTION

  UPDATE accounts SET balance = balance - 1000 WHERE id = 1;
  UPDATE accounts SET balance = balance + 1000 WHERE id = 2;

COMMIT;   -- save both changes

-- If error occurs:
ROLLBACK;  -- undo everything since BEGIN

-- Savepoint
SAVEPOINT my_save;
ROLLBACK TO my_save;

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