先对Inventory表SUM,然后再JOINselect from aaa left join (select id,sum() from Inventory group by ..) x
select A.id,A.qty as 总数量,B.qty as 库存量,A.qty-B.qty as 未入库量,C.qty as 销售量 from product A left join (select product_id,sum(qty) as qty from invertory group by product_id)B on A.id = B.prduct_id left join sell C on A.id = C.id
from aaa left join (select id,sum() from Inventory group by ..) x
from product A left join (select product_id,sum(qty) as qty from invertory group by product_id)B
on A.id = B.prduct_id left join sell C on A.id = C.id
回复 zczhangchao2003: Product表 和 Inventory表 和 Sell表的qry字段有啥关系