mysql分组，取每组前几条记录

SELECT  * FROM 表名 a
WHERE (SELECT count(*) FROM 表名 b WHERE b.日期=a.日期 AND b.id>a.id  )<5
 ORDER BY 日期 asc,id desc

SELECT * from sales_bestsellers_aggregated_daily AS t1
where
(SELECT COUNT(*) FROM sales_bestsellers_aggregated_daily AS t2 WHERE t2.period=t1.period AND qty_ordered>t1.qty_ordered) < 10
AND period >= '2016-03-01' AND period <= '2016-03-02' AND store_id=1
ORDER BY t1.period,t1.qty_ordered DESC;