mysql中两表更新时产生的奇葩问题，产生死锁！

Posted 2020-08-16 Greyed Wolf

如下一个两表更新语句

UPDATE hzxm201610 a,xmhzylb1201610 b SET a.gk07_1_6=b.gk04_11,a.gk07_2_6=b.f06_1,a.gk07_3_6=b.f07_1,a.gk07_4_6=b.f08_1  where   substring(a.gk01,1,4) in (‘5323‘) and a.gk01=b.gk01 and dqdm=‘532300‘

如果漏掉了where会怎么样：

UPDATE hzxm201610 a,xmhzylb1201610 b SET a.gk07_1_6=b.gk04_11,a.gk07_2_6=b.f06_1,a.gk07_3_6=b.f07_1,a.gk07_4_6=b.f08_1  substring(a.gk01,1,4) in (‘5323‘) and a.gk01=b.gk01 and dqdm=‘532300‘

一般以为是会报错。其实不然，这个语句正常执行！而且对两个表全扫描，最后什么也不做！但是会锁定两个表很长时间，导致应用系统无法工作！

查询mysql死锁的语句：

#Show PROCESSLIST;
SELECT * FROM information_schema.INNODB_TRX;
SELECT * FROM information_schema.INNODB_LOCKS;
SELECT * FROM information_schema.INNODB_LOCK_WAITS;
SHOW VARIABLES LIKE ‘%lock%‘;