mysql分组后限制条数和排序

废话少数直接上需求和解决方案

需求：分组查询指定条数

这是我的表

表名news，查询class_id为1和2的数据各三条

这是sql：

select n1.* from news n1
where n1.`class_id` in (1,2)
group by n1.`class_id`,n1.id having (select count(n2.id) from news n2 where n2.class_id=n1.class_id and n2.id>=n1.id)<=3 order by n1.class_id desc