主题：select语句

Select a.bh as 产品编号, a.mc as 名称, sum(b.sl) As 出库数量, sum(b.sl) As 入库数量

fro m cp a

left join ck b on a.bh = b.bh

left join rk c on a.bh = c.bh

group by a.bh, a.mc

 sum(b.sl) As 出库数量, sum(c.sl) As 入库数量