Sql语句的优化

最新推荐文章于 2022-10-31 18:41:45 发布

pilqc2009

最新推荐文章于 2022-10-31 18:41:45 发布

阅读量299

点赞数

CC 4.0 BY-SA版权

分类专栏： SQL

本文链接：https://blog.youkuaiyun.com/pilqc2009/article/details/8176624

SQL 专栏收录该内容

2 篇文章

订阅专栏

select num form a where num not in(select num from b)
优化如下：
select num from a where exists(select 1 from b where num =a.num)

delete from acct_item where subs_id not in(select subs_id from subs);
优化如下：
delete from acct_item a where not exists (select 1 from subs b where a.subs_id=b.subs_id )

select * from em where deptno>3;
优化如下：
select * from em where deptno>=4;

select * from kj_dept where dept_id in(select dept_id from kj_dept_info where dept_id =xxx)
优化如下：
select * from kj_dept where exists (select * from kj_dept_info where kj_dept.dept_id = kj_dept_info.dept_id and dept_id = xxx)

select * from employee where salary <>3000;
优化如下：
select * from employee where salary<3000 or salary>3000;