select b.prodnum,sum(b.quantity*c.unitprice)from orders a join items b on a.ordernum=b.ordernum join products c on b.prodnum=c.prodnumwhere month(a.orderdate)=5group by b.prodnummonth(a.orderdate)=5可换成datepart(mm,a.orderdate) 如果需要按照不同的供应商统计select b.prodnum,b.suppcode,sum(b.totalprice)from orders a join items b on a.ordernum=b.ordernum join products c on b.prodnum=c.prodnumwhere month(a.orderdate)=5group by b.prodnum,b.suppcode如果需要名字，只要加在group by 后面