大量的left join 怎么优化select a.id,a.num,b.num,b.pcs,c.num,c.pcs,d.num,d.pcs,e.num,e.pcs,a.x,a.y from a left join b.id=a.id and b.time=a.timeleft join c.id=a.id and b.time=a.timeleft join d.id=a.id and b.time=a.timeleft join e.id=a.id and b.t

大量的left join 怎么优化select a.id,a.num,b.num,b.pcs,c.num,c.pcs,d.num,d.pcs,e.num,e.pcs,a.x,a.y from a left join b.id=a.id and b.time=a.timeleft join c.id=a.id and b.time=a.timeleft join d.id=a.id and b.time=a.timeleft join e.id=a.id and b.t left join 优化如图.左边是我查出来的.用哪种可以查出来右边的哪种结构. 删除怎么用left join inner join和left join的区别 left join和inner join的区别 left join 和 left outer join 的区别 left join 和 left outer join 的区别 left join 和 left outer join 的区别 SQL中 inner join、 left join 、right join、 outer join之间的区别 inner join,left join,right join,full join 的区别?最好用例子说明! sql中left join from 多个表怎么写select * from a,b,c,d LEFT JOIN e on e.id=a.id left join f on f.id=c.id现在这句是错的,怎么写才正确 join的过去式七年下同步优化里的 sql表连接查询的区别`inner join、left join、rightjoin、outer join举例说明· 数据库的问题：解释inner join,left outer join ,cross join 数据库中的left join 和left outer join有什么本质的区别? 录音笔上的sel是什么意思 linq用lambda表达式 left join 自连接怎么写 left join 和 right jion 怎么表示 LINQ