Reputation: 457
I am trying to get a list of the last 10 Serial numbers from a table of Test information on SQL Server 2005. I tried something like this:
SELECT DISTINCT TOP (10) Serial, DateTime
FROM [Test].[dbo].[TestInfo]
WHERE (TestedBy = 'JSMITH') ORDER BY DateTime DESC
which returns duplicate Serials:
+---------+-------------------------+
| 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 |
+---------+-------------------------+
Is there a way, either using a query or sub-query to get the last 10 Serials without duplicates?
Upvotes: 1
Views: 166
Reputation: 911
Probably something like:
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
Upvotes: 1
Reputation: 86892
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
Upvotes: 1
Reputation: 2194
it return duplicate rows beacuse the datetime is different for each row. if you need only the serial field you must write only Serial field in the query.
Upvotes: -1
Reputation: 26694
select top (10) Serial, Max(DateTime)
from [Test].[dbo].[TestInfo]
where (TestedBy = 'JSMITH')
group by Serial
order by Max(DateTime) desc
Upvotes: 5