mysql 數據庫group by 按排序取值
mysql 5.7 以后，group by 想要按照排序的順序來取值，在子結果集中要有union,group by 等操作，不然按照id默認排序來取值
示例：
數據庫：
score表
id user_id num
1 100 95
2 100 96
3 101 97
4 101 95
select * from score group by user_id order by num desc
結果
id user_id num
3 101 97
1 100 95
select * from
(select * from score group by id order by num desc) f
group by user_id order by num desc
結果
id user_id num
3 101 97
2 100 96