跪求一个left join 的sql语句写法
表goods: gid | name
1 xde
2 dfdd
3 东方古国风格
表glist: lid | gid | subname | displayorder
1 1 三三四四 2
2 1 扫扫地 12
3 2 日方非法 10
4 2 到噶多个 1
我现在想取出glist表中的lid为2,3两项。
但是SELECT g . * , f . * FROM goods g LEFT JOIN glist f ON g.gid = f.gid ORDER BY g.displayorder DESC limit 2 这个sql取出的结果是错误的。
按照goods中的gid升序 取出两条 同时也取出在glist中属于相应gid的一条(取displayorder值最大的一个)
结果应为goods中的1,2 同时也取出glist中的2,3
------解决方案--------------------
可以这么写select a.*,max(b.displayorder),b.subname from goods as a left join glist as b on a.gid=b.gid group by a.gid
分组查询displayorder字段最大值
------解决方案--------------------
SELECT g . * , f . * FROM goods g LEFT JOIN glist f ON g.gid = f.gid ORDER BY f.displayorder DESC limit 2
你的sql有问题,不是g,是f。但是这样不能满足你以下要求
“按照goods中的gid升序 取出两条 同时也取出在glist中属于相应gid的一条(取displayorder值最大的一个)
结果应为goods中的1,2 同时也取出glist中的2,3”
楼上也是错的,虽然max(b.displayorder)取出来是对的,但是b.subname不对。
正确的应该是:
select * from (select g.gid, g.name, f.lid,f.subname,f.displayorder from goods g left join glist f on g.gid=f.gid order by g.gid ASC, f.displayorder DESC) h group by h.gid LIMIT 2

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