优化前 select * from user where xx=1 limit 10,10
优化后 select * from user a inner join (select id from user where xx=1 order by id limit 10,10) b using(id)
优化前 select * from user where xx=1 limit 10,10
优化后 select * from user a inner join (select id from user where xx=1 order by id limit 10,10) b using(id)