Aislamiento
READ COMMITTED, REPEATABLE READ, SERIALIZABLE.
Entiende dirty reads, non-repeatable reads y phantom reads para elegir nivel correcto.
Transacción con aislamiento
SET TRANSACTION ISOLATION LEVEL READ COMMITTED;
START TRANSACTION;
UPDATE cuentas SET saldo = saldo - 100 WHERE id = 1;
UPDATE cuentas SET saldo = saldo + 100 WHERE id = 2;
COMMIT;