最近碰到这样一个SQL引发的性能问题，SQL内容大致如下： 1 2 3 4 5 6 7 SELECT * FROM t1 WHERE id = 999 AND (case $1 WHEN true THEN info = $2 ELSE info = $3 end) limit 1; 开发反应这条SQL加上limit 1之后过了一段时
1. union合并查询结果集 查询工作岗位是 MANAGER 和 SALESMAN 的员工？ 1 mysql select ename, job from emp where job = MANAGER or job = SALESMAN; 1 mysql select ename, job from emp where job in(MANAGER, SALESMAN); 1 mysql sele
首先说明一下MySQL的版本： mysql select version();+-----------+| version() |+-----------+| 5.7.17 |+-----------+1 row in set (.00 sec) 表结构： mysql desc test;+--------+---------------------+------+-----+---------+----------------+| Field
错误的写法： select id=queryMyApplicationRecord parameterType=MyApplicationRequest resultMap=myApplicationMap SELECT a.*, FROM tb_user a WHERE 1=1 if test=ids != null and ids.size()!=0 AND a.id IN foreach collection=ids item=id index=index
