select *from employees order by name limit 10000,5;
--优化后
select *from employees e inner join(select id from employees order by name limit 10000,5) ed on e.id = ed.id
join关联查询优化
NLJ算法
关联的被驱动表带索引
BNL算法
关联的被驱动表不带索引
straight_join指定关联的驱动表
in和exists
select *from A where id in (select id from B)
select *from A where exists (select 1 from B where A.id = B.id)
