帮我看下SQL语句错在哪里

帮我看下SQL语句错在哪里select a.comid as 货号,a.barcode as 条码,sum(b.stock_qty) as 总库存,sum(c.sale_qnty) as 总销售fromtemp01 a left join bwsyv9_01.dbo.ic_t_branch_stock b on(a.item_no = b.item_no ) left join bwsyv9_01.dbo.pos_t_saleflow c on(a.item_no = c.item_no)wherea.yesno ='0'group bya.comid,a.barcodeselect a.comid as 货号,a.barcode as 条码,sum(b.stock_qty) as 总库存数,sum(c.sale_qnty) as 总销售fromtemp01 a,bwsyv9_01.dbo.pos_t_saleflow c,bwsyv9_01.dbo.ic_t_branch_stock bwhere(a.item_no = c.item_no and a.item_no = b.item_no) and a.yesno ='0'group bya.comid,a.barcode这两个语句都有同样一个错误 SUM()函数内统计的数量完全不正确我用商品资料表同时结联了一个库存与一个销售表 之后查出来就不正确了(SUM统计的库存与销售都是多倍的)如果我只用一个JOIN(结联一个表)就不会出现这种问题帮我看下错在哪里?