状态查看与事务要点
- 看服务器状态：SHOW STATUS; 看警告：SHOW WARNINGS;
- 看错误：SHOW ERRORS; 看引擎事务状态：SHOW ENGINE INNODB STATUS;
- 开事务：START TRANSACTION; 或 BEGIN;
- 提交：COMMIT; 回滚：ROLLBACK;
- 锁表：LOCK TABLES 表名 WRITE/READ; 释放：UNLOCK TABLES;
- 设隔离级别：SET TRANSACTION ISOLATION LEVEL 级别;
状态查看与事务示例
SHOW STATUS;
SHOW WARNINGS;
SHOW ENGINE INNODB STATUS;
-- 把两笔转账绑成一个事务
START TRANSACTION;
UPDATE accounts SET balance = balance - 100 WHERE id = 1;
UPDATE accounts SET balance = balance + 100 WHERE id = 2;
COMMIT;
-- 出问题就 ROLLBACK;
LOCK TABLES orders WRITE;
-- 处理独占写
UNLOCK TABLES;
避坑提醒：SHOW ENGINE INNODB STATUS 是排查锁等待和长事务的金矿，但输出很长，重点看 TRANSACTIONS 段里『等待锁』和『持有锁』的那些行。
