常见SQL注入模式
SELECT * FROM users WHERE username = 'admin' OR '1'='1'
SELECT * FROM users WHERE id = '1' OR 1=1 --
SELECT * FROM users WHERE username = 'admin' UNION SELECT password FROM users
SELECT * FROM users WHERE id = '1' DROP TABLE users --
SELECT * FROM users WHERE username = 'admin' AND (SELECT COUNT(*) FROM admin) > 0