user1.sql

START TRANSACTION ;

SELECT * FROM guestbooks;

UPDATE guestbooks
SET title = 'Diubah Oleh User 1'
WHERE id = 9;

COMMIT;

START TRANSACTION ;

SELECT * FROm products;

SELECT * FROM products WHERE id = 'P0001' FOR UPDATE;

UPDATE products
SET quantity = quantity - 10
WHERE id = 'P0001';

COMMIT ;

#  DEADLOCK

START TRANSACTION ;

SELECT * FROM products WHERE id = 'P0001' FOR UPDATE ;

SELECT * FROM products WHERE id = 'P0002' FOR UPDATE ;

# LOCK TABLE READ

LOCK TABLES products READ;

UPDATE products
SET quantity = 100
WHERE id = 'P0001';

UNLOCK TABLES ;

# LOCK TABLE WRITE

LOCK TABLES products WRITE ;

UPDATE products
SET quantity = 100
WHERE id = 'P0001';

SELECT * FROM products;

UNLOCK TABLES ;

# LOCK INSTANCE

LOCK INSTANCE FOR BACKUP;

UNLOCK INSTANCE;