CREATE TABLE accounts ( 
  number INT, 
  balance FLOAT, 
  PRIMARY KEY(number) 
) ENGINE InnoDB; 

INSERT INTO accounts(number, balance) VALUES(12345, 1025); 
INSERT INTO accounts(number, balance) VALUES(67890, 140); 

BEGIN;
SELECT balance FROM accounts WHERE number=12345 FOR UPDATE;
UPDATE accounts SET balance=balance+25 WHERE number=12345;
COMMIT;

BEGIN;
UPDATE accounts SET balance=balance-250 WHERE number=12345;
UPDATE accounts SET balance=balance+250 WHERE number=67890;
SELECT * from accounts;
ROLLBACK;



BEGIN;
SELECT balance FROM accounts WHERE number=12345 FOR UPDATE;

BEGIN;
SELECT balance FROM accounts WHERE number=12345 FOR UPDATE;



BEGIN;
UPDATE accounts SET balance=balance-250 WHERE number=12345;

BEGIN;
UPDATE accounts SET balance=balance-250 WHERE number=12345;


BEGIN;
SELECT balance FROM accounts WHERE number=12345 FOR UPDATE;
SELECT balance FROM accounts WHERE number=67890 FOR UPDATE;

BEGIN;
SELECT balance FROM accounts WHERE number=67890 FOR UPDATE;
SELECT balance FROM accounts WHERE number=12345 FOR UPDATE;