场景:ide
查询出 图书和食品两个分类(或多个分类) 在最新的一天内的商品销售状况 it
select a.* from prod_sales a INNER JOINclass
(select prod_class,max(sales_date) as sn from prod_salesdate
GROUP BY prod_class) b select
on a.prod_class=b.prod_class and a.sales_date=b.sn order by prod_class查询