[英]SQL Query/Sub-query help needed
我試圖從SQL Server 2005上的測試信息表中獲取最后10個序列號的列表。我嘗試了以下操作:
SELECT DISTINCT TOP (10) Serial, DateTime
FROM [Test].[dbo].[TestInfo]
WHERE (TestedBy = 'JSMITH') ORDER BY DateTime DESC
返回重復的序列號:
+---------+-------------------------+
| Serial | DateTime |
+-----------------------------------+
| 1114048 | 2011-03-16 11:03:14.000 |
| 1617683 | 2011-03-11 15:07:29.000 |
| 1617683 | 2011-03-11 15:07:27.000 |
| 1617683 | 2011-03-11 15:07:26.000 |
| 1617683 | 2011-03-10 13:16:04.000 |
| 1617683 | 2011-03-10 13:15:35.000 |
| 1617683 | 2011-03-10 13:15:30.000 |
| 1617683 | 2011-03-07 13:42:48.000 |
| 1617683 | 2011-03-07 13:40:32.000 |
| 1617683 | 2011-03-07 13:37:58.000 |
+---------+-------------------------+
有沒有辦法使用查詢或子查詢來獲取最后10個序列號而不重復的序列號?
select top (10) Serial, Max(DateTime)
from [Test].[dbo].[TestInfo]
where (TestedBy = 'JSMITH')
group by Serial
order by Max(DateTime) desc
SELECT TOP 10
*
FROM (SELECT
Serial,
MAX(DateTime) AS DateTime
FROM [Test].[dbo].[TestInfo]
WHERE (TestedBy = 'JSMITH')
GROUP BY Serial) q1
ORDER BY q1.DateTime DESC
大概是這樣的:
SELECT DISTINCT TOP (10) Serial, DateTime
FROM (
SELECT Serial, MAX(DateTime) AS DateTime
FROM [Test].[dbo].[TestInfo]
WHERE (TestedBy = 'JSMITH')
GROUP BY Serial
) AS sub
ORDER BY DateTime DESC
它返回重復的行,因為每一行的日期時間都不相同。 如果僅需要串行字段,則必須在查詢中僅寫入串行字段。
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