我必须为每个主题选择最后两条记录。
例如: 表:消息
id | topic_id
------------
1 | 1
2 | 1
3 | 1
4 | 1
5 | 2
6 | 2
7 | 2
8 | 3
9 | 3
10 | 3
我想获取这些行:
3 1
4 1
6 2
7 2
9 3
10 3
我该怎么做?
最佳答案
SELECT max(id), max(topic_id) FROM msg
GROUP BY topic_id
UNION
SELECT max(id), max(topic_id) FROM msg
WHERE id not in (
SELECT max(id) as id FROM msg
GROUP BY topic_id)
GROUP BY topic_id
关于sql - MySQL中如何为每个topic_id选择最后两条记录,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/2596489/