Exclude duplicates, keep the value with the latest date

Question

Exclude duplicates, keep the value with the latest date

SqlHomebrewer

SSC Eights!

Points: 874
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February 25, 2013 at 4:31 pm

#274560

I'm trying to create a query with multiple columns. The CandidateID column includes values that appear more than once. I need my query to return the latest CandidateID value and to exclude the older CandidateID values of the same ID number.
Sample values:
2008432012-02-14 07:49:00
2008432012-02-15 06:56:00
2310222012-02-14 07:49:00
2335252012-01-30 21:15:00
2766992012-01-30 21:14:00
2910192012-01-30 21:15:00
2988052012-01-30 21:15:00
2988052012-02-15 06:56:00
2988052012-02-21 09:39:00
3060112012-02-14 07:49:00
3060112012-02-15 06:56:00
3060112012-02-21 09:55:00
3135382012-01-30 21:15:00
3161352012-01-30 21:14:00
I need the query to return the following...
2008432012-02-15 06:56:00
2310222012-02-14 07:49:00
2335252012-01-30 21:15:00
2766992012-01-30 21:14:00
2910192012-01-30 21:15:00
2988052012-02-21 09:39:00
3060112012-02-21 09:55:00
3135382012-01-30 21:15:00
3161352012-01-30 21:14:00
"Nicholas"

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Sean Lange SSC Guru Points: 286590 More actions · Answer 1

5280_Lifestyle (2/25/2013)
I'm trying to create a query with multiple columns. The CandidateID column includes values that appear more than once. I need my query to return the latest CandidateID value and to exclude the older CandidateID values of the same ID number.

Like this?

select CandidateID, max(YourDateColumn)

from YourTable

group by CandidateID

_______________________________________________________________

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Need to split a string? Try Jeff Modens splitter http://www.sqlservercentral.com/articles/Tally+Table/72993/.

Cross Tabs and Pivots, Part 1 – Converting Rows to Columns - http://www.sqlservercentral.com/articles/T-SQL/63681/
Cross Tabs and Pivots, Part 2 - Dynamic Cross Tabs - http://www.sqlservercentral.com/articles/Crosstab/65048/
Understanding and Using APPLY (Part 1) - http://www.sqlservercentral.com/articles/APPLY/69953/
Understanding and Using APPLY (Part 2) - http://www.sqlservercentral.com/articles/APPLY/69954/

Kingston Dhasian SSCoach Points: 19799 More actions · Answer 2

You can also use ROW_NUMBER()

SELECT*

FROM(

SELECTROW_NUMBER() OVER ( PARTITION BY CandidateID ORDER BY YourDateColumn DESC ) AS RN, *

FROMYourTable

) AS YT

WHEREYT.RN = 1

Kingston Dhasian

How to post data/code on a forum to get the best help - Jeff Moden
http://www.sqlservercentral.com/articles/Best+Practices/61537/

BriPan SSCrazy Points: 2061 More actions · Answer 3

but If performance is in concern then go for

select CandidateID, max(YourDateColumn)

from YourTable

group by CandidateID

ChrisM@Work SSC Guru Points: 186127 More actions · Answer 4

BriPan (2/26/2013)
but If performance is in concern then go for
select CandidateID, max(YourDateColumn)
from YourTable
group by CandidateID

Sean's solution is almost certainly quicker than Kingston's ROW_NUMBER method; however, Kingston's solution is a viable alternative which introduces the method to those who may not already be familiar with it - and of course, it demonstrates how to identify the target rows without necessarily filtering out those which are not targeted.

^{“Write the query the simplest way. If through testing it becomes clear that the performance is inadequate, consider alternative query forms.” - Gail Shaw}

For fast, accurate and documented assistance in answering your questions, please read this article.
Understanding and using APPLY, (I) and (II) Paul White
Hidden RBAR: Triangular Joins / The "Numbers" or "Tally" Table: What it is and how it replaces a loop Jeff Moden

SqlHomebrewer SSC Eights! Points: 874 More actions · Answer 5

Sean's solution worked. Thank you very much!

"Nicholas"

Sean Lange SSC Guru Points: 286590 More actions · Answer 6

5280_Lifestyle (2/26/2013)
Sean's solution worked. Thank you very much!

You are quite welcome. Glad that worked for you.

_______________________________________________________________

Need help? Help us help you.

Read the article at http://www.sqlservercentral.com/articles/Best+Practices/61537/ for best practices on asking questions.

Need to split a string? Try Jeff Modens splitter http://www.sqlservercentral.com/articles/Tally+Table/72993/.

Cross Tabs and Pivots, Part 1 – Converting Rows to Columns - http://www.sqlservercentral.com/articles/T-SQL/63681/
Cross Tabs and Pivots, Part 2 - Dynamic Cross Tabs - http://www.sqlservercentral.com/articles/Crosstab/65048/
Understanding and Using APPLY (Part 1) - http://www.sqlservercentral.com/articles/APPLY/69953/
Understanding and Using APPLY (Part 2) - http://www.sqlservercentral.com/articles/APPLY/69954/