1) select * from 订单 where 订购日期 between '1997/10/1' and '1997/12/31'; 2) select * from 订单明细 as A inner join 订单 as B on a.订单ID=b.订单ID where B.订购日期 between '1998/01/01' and '1998/03/31'; 3) select sum(A.单价*A.数量*A.折扣) as 总金额 from 订单明细 as A inner join 订单 as B on A.订单ID=B.订单ID where B.订购日期 between '1998/01/01' and '1998/01/31'; 4) select A.产品ID,sum(A.单价*A.数量*A.折扣) as 金额 from 订单明细 as A inner join 订单 as B on A.订单ID=B.订单ID where B.订购日期 between '1998/01/01' and '1998/12/31' group by A.产品ID