举一个评论的例子
表的数据
id name common time
1 qq qqq 2018-05-07 16:45:23
2 qq wwww 2018-05-17 16:45:50
3 ww ssssss 2018-05-14 16:46:09
4 ww dddddd 2018-05-18 16:46:28
5 qq ccccccc 2018-05-23 17:25:16查询相同用户最新评论
select * from user x where time = (select max(time) from user y where x.name=y.name);结果
+----+------+---------+---------------------+
| id | name | common | time |
+----+------+---------+---------------------+
| 4 | ww | dddddd | 2018-05-18 16:46:28 |
| 5 | qq | ccccccc | 2018-05-23 17:25:16 |
+----+------+---------+---------------------+解释
user x 是查询所有的数据
max(time)取出最大的时间来
y.name = x.name 查询哪个用户