Question

如果已经发布或在互联网上发布，我很抱歉。我经过长时间的搜索来到这里

假设这是表格：

+----+-------+----------+---------------------+
| id | name  | group_id | created_time        |
+----+-------+----------+---------------------+
|  1 | foo   | 1        | 2010-09-22 00:00:00 |
|  2 | rafi  | 2        | 2010-09-23 00:00:00 |
|  3 | rafi1 | 2        | 2010-09-24 00:00:00 |
|  4 | rafi2 | 2        | 2010-09-25 00:00:00 |
|  5 | bar   | 5        | 2010-09-26 00:00:00 |
|  6 | baz   | 6        | 2010-09-27 00:00:00 |
|  7 | baz1  | 6        | 2010-09-26 00:00:00 |
|  8 | rafi3 | 2        | 2010-09-24 00:00:00 |
|  9 | baz2  | 6        | 2010-09-30 00:00:00 |
+----+-------+----------+---------------------+

我想要的是根据组ID对它们进行分组，并按created_time desc（较新的第一个）命令

但是当我说

时

SELECT id,name,group_id,created_time FROM test group by group_id ORDER BY id desc;

我明白了

+----+------+----------+---------------------+
| id | name | group_id | created_time        |
+----+------+----------+---------------------+
|  6 | baz  | 6        | 2010-09-27 00:00:00 |
|  5 | bar  | 5        | 2010-09-26 00:00:00 |
|  2 | rafi | 2        | 2010-09-23 00:00:00 |
|  1 | foo  | 1        | 2010-09-22 00:00:00 |
+----+------+----------+---------------------+

我想要的是得到这样的东西

+----+------+----------+---------------------+
| id | name | group_id | created_time        |
+----+------+----------+---------------------+
|  9 | baz2 | 6        | 2010-09-30 00:00:00 |
|  5 | bar  | 5        | 2010-09-26 00:00:00 |
|  5 | rafi2| 2        | 2010-09-25 00:00:00 |
|  1 | foo  | 1        | 2010-09-22 00:00:00 |
+----+------+----------+---------------------+

我试过了

SELECT max(date(created_time)) as foo,name,group_id FROM test group by group_id ORDER BY foo desc;

我得到了正确的日期但却无法说出正确的名称。

Answer 1

该查询是否符合您的需求？

SELECT t1.id, t1.name, t1.group_id FROM Test t1
INNER JOIN
  (SELECT MAX(id) as maxid FROM Test GROUP BY group_id) t2
ON t2.maxid = t1.id
ORDER BY t1.id DESC;

修改

如果您想按日期时间字段排序，可以稍微修改上面的查询：

SELECT t1.id, t1.name, t1.group_id, t1.created_date FROM Test t1 INNER JOIN (SELECT MAX(created_date) as maxdate, group_id FROM Test GROUP BY group_id) t2 ON (t2.maxdate = t1.created_date AND t2.group_id = t1.group_id) ORDER BY t1.created_date DESC;

它仍然是你在找什么？

Answer 2

这个怎么样？使用子查询是一个选项 - 如果是这样，这可能会起作用！

SELECT id, name, group_id WHERE id IN (Select max(id) FROM test group by group_id) ORDER BY id desc;

按列修改组以获得最新结果

2 个答案: