Question

我想限制每个DeviceId＆amp;的x最后几天这个选择的ID：

SELECT DeviceId, Id, MAX(DateAndTime) as 'DateAndTime'
FROM EventAndMessage
GROUP BY DeviceId, Id
ORDER BY DateAndTime DESC`

结果示例：

DeviceId            Id      DateAndTime
00:11:22:33:44:55   00D330  2018-05-25 15:41:10.620
00:03:4F:00:10:94   027286  2018-05-11 09:23:26.927
00:03:4F:00:10:94   0351DE  2018-05-11 09:23:13.690
00:03:4F:00:10:94   0351DE  2018-05-11 09:23:09.747
00:03:4F:00:10:94   0351DE  2018-05-11 09:23:01.797
00:03:4F:00:10:94   0351C4  2018-05-11 09:22:47.633

在这个例子中，我想限制2个最年轻的记录。注意：2应该是我可以更改的参数。

然后应该是正确的结果：

DeviceId            Id      DateAndTime
00:11:22:33:44:55   00D330  2018-05-25 15:41:10.620
00:03:4F:00:10:94   027286  2018-05-11 09:23:26.927
00:03:4F:00:10:94   0351DE  2018-05-11 09:23:13.690
00:03:4F:00:10:94   0351DE  2018-05-11 09:23:09.747
00:03:4F:00:10:94   0351C4  2018-05-11 09:22:47.633

由于

Answer 1

Oracle 12c及更高版本 -

SELECT DeviceId, Id, MAX(DateAndTime) as 'DateAndTime'
FROM EventAndMessage
GROUP BY DeviceId, Id
ORDER BY DateAndTime DESC
FETCH FIRST X ROWS ONLY;

如何限制每个设备的x最后几天结果的选择

1 个答案: