数据库事务。

案例是 Alice 转账给 Bob。

Basic

BEGIN;
UPDATE accounts SET balance = balance - 100.00
    WHERE name = 'Alice';
UPDATE accounts SET balance = balance + 100.00
    WHERE name = 'Bob';
COMMIT;

Savepoints

BEGIN;
UPDATE accounts SET balance = balance - 100.00
    WHERE name = 'Alice';
SAVEPOINT my_savepoint;
UPDATE accounts SET balance = balance + 100.00
    WHERE name = 'Bob';
-- oops ... forget that and use Wally's account
ROLLBACK TO my_savepoint;
UPDATE accounts SET balance = balance + 100.00
    WHERE name = 'Wally';
COMMIT;