Question

这就是我现在在查询中的内容：

+--------------------+-----------+------------+
| status             | entity_id | seconds    |
+--------------------+-----------+------------+
| Submitted          |       494 | 1352102400 |
| Accepted           |       494 | 1352275200 |
| In press/e-publish |       494 | 1352966400 |
| Rejected           |       520 | 1355817600 |
| Accepted           |       570 | 1352102400 |
+--------------------+-----------+------------+

我希望它看起来像：

+--------------------+-----------+------------+
| status             | entity_id | seconds    |
+--------------------+-----------+------------+
| In press/e-publish |       494 | 1352966400 |
| Rejected           |       520 | 1355817600 |
| Accepted           |       570 | 1352102400 |
+--------------------+-----------+------------+

在准SQL中：

SELECT status, entity_id, MAX(seconds) 
FROM foo
GROUP BY entity_id, seconds

上面的准SQL看起来是正确的，但“status”列值与正确的行不对应。我得到了类似下面的内容：

+--------------------+-----------+------------+
| status             | entity_id | seconds    |
+--------------------+-----------+------------+
| Submitted          |       494 | 1352966400 |
| Rejected           |       520 | 1355817600 |
| Accepted           |       570 | 1352102400 |
+--------------------+-----------+------------+

Answer 1

未经测试，但应该看起来像这样：

SELECT status, entity_id, seconds
FROM entities E
WHERE E.seconds == (
  SELECT MAX(E2.seconds)
  FROM entities E2
  WHERE E2.entity_id = E.entity_id
)

（为你的问题设置一个SQLfiddle会给你一个更加测试的答案：p）

Answer 2

以下查询将给出您的预期结果。

SELECT max(maxsec), status, entity_id from 
(SELECT status, entity_id, MAX(seconds)  as maxsec
FROM table1
GROUP BY entity_id,status) a GROUP BY entity_id

您的架构已创建here。

MySQL：选择MAX值并进行分组

2 个答案: