kk Blog —— 通用基础

date [-d @int|str] [+%s|"+%F %T"]

mysql 分组后的组内排序

方法一

https://www.cnblogs.com/hxfcodelife/p/10226934.html

数据库的查询顺序是先分组的,最后才将结果进行排序。 group by XX order by yy 是不行的

用 row_number() over(partition by XX order by YY desc)

1
select a.Classid,a.English from (select Classid,English,row_number() over(partition by Classid order by English desc) as n from CJ) a where n<=2

方法二

https://blog.csdn.net/u014508939/article/details/100561133

用 GROUP_CONCAT, SUBSTRING_INDEX

1
SELECT SUBSTRING_INDEX(GROUP_CONCAT(id, ORDER BY update_time DESC), ',', 1) FROM goods GROUP BY good_id OEDER by update_time DESC;