[英]Mysql - How to get last record using GROUP BY
我有一个如下表:
id | deptid | last_activities
1 | 1 | MMD PURCASHING
2 | 1 | JKO / REPORTING
3 | 2 | STAND BY CC
4 | 3 | JKO / REPORTING
我的查询:
SELECT id, deptid, last_activities FROM dept_activities GROUP BY deptid ORDER BY id DESC
结果如下:
id | deptid | last_activities
4 | 3 | JKO / REPORTING
3 | 2 | STAND BY CC
1 | 1 | MMD PURCASHING
在那里我想要这样的结果:
id | deptid | last_activities
4 | 3 | JKO / REPORTING
3 | 2 | STAND BY CC
2 | 1 | JKO / REPORTING
怎么会这样? 如何正确查询?
请尝试这个:
SELECT * FROM dept_activities AS da1
JOIN
(SELECT MAX(id) as max_id FROM dept_activities GROUP BY deptid DESC) AS da2
ON (da1.id = da2.max_id);
使用子查询获取每个deptid的最大ID,然后将其与表结合在一起,可以得到如下信息:
SELECT a.id, a.deptid, a.last_activities
FROM dept_activities a
INNER JOIN
(
SELECT MAX(id) AS MaxId, deptid
FROM dept_activities
GROUP BY deptid
) Sub1
ON a.deptid = Sub1.deptid
AND a.id = Sub1.MaxId
ORDER BY a.id DESC
使用GROUP_CONCAT的另一种可能的解决方案,尽管并不热衷于此(如果last_activity包含用于GROUP_CONCAT的定界符,它将失败。
SELECT MAX(id), deptid, SUBSTRING_INDEX(GROUP_CONCAT(last_activities ORDER BY id DESC), ',', 1)
FROM dept_activities
GROUP BY a.deptid
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