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Access Query to Select the 2 Most Recent Records of Each ClientID.

Posted on 2013-01-25
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Last Modified: 2013-01-29
Good afternoon Experts,

I need a query that will select the 2 most recent records for each Client_ID, based on the date in the update_date_utc field. There may be 1, 2, 3, or more instances of each Client_ID. If only 1 instance exists, I don't want it selected. If 2 instances exist, I want both instances selected, and if 3 or more instances exist, I want the 2 most recent instances based on the date in the update_date_utc field. See attached spreadsheet.

Thanks in advance for your help.
Craig
ChangeOwner.xls
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Comment
Question by:CraigMan
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7 Comments
 
LVL 61

Expert Comment

by:mbizup
ID: 38820995
Try this:

SELECT t.client_id, t.user_name, t.update_date_utc
FROM tblClients t
WHERE t.client_id IN (
        SELECT TOP 2 cdupe.client_id 
        FROM tblClients cdupe 
        WHERE cdupe.client_id  = t.client_id  AND  cdupe.client_id  IN 
               (SELECT c.client_id
                FROM tblClients c
                GROUP BY c.client_id
                HAVING Count(c.user_name) > 1) 
        ORDER BY cdupe.update_date_utc DESC
)

Open in new window


And take a look at the following article under the heading "top N records per group":
http://allenbrowne.com/subquery-01.html

This is a variation on that, with the HAVING clause limiting the output to groups of two or more.

You may have to replace occurrences of tblClients with your own table name.
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LVL 31

Expert Comment

by:hnasr
ID: 38822998
Removed comment, not for this question.
0
 

Author Comment

by:CraigMan
ID: 38831204
mbixup,

Your solution did eliminate the single instances of client_id, but did not limit the result to the 2 most current records per client_id, if more than 2 instances exist. How do I limit output to 2 most current records?

Craig
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LVL 61

Accepted Solution

by:
mbizup earned 2000 total points
ID: 38831450
Here you go...

SELECT t.client_id, t.user_name, t.update_date_utc
FROM tblClients AS t
WHERE (t.client_id &  t.update_date_utc) IN  
(
        SELECT TOP 2 cdupe.client_id & cdupe.update_date_utc 
        FROM tblClients cdupe 
        WHERE cdupe.client_id  =  t.client_id  and  cdupe.client_id  IN 
               (SELECT c.client_id
                FROM tblClients c
                GROUP BY c.client_id
                HAVING Count(c.user_name) > 1) 
        ORDER BY cdupe.update_date_utc DESC
) 

Open in new window


Try Query1 in the attached  DB
db2.mdb
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LVL 31

Expert Comment

by:hnasr
ID: 38832067
Try this:
For table a(aid, f1, f2) - aid is the primary key.
aID      f1      f2
1      1      1
2      1      2
3      1      3
4      2      2
5      4      3
6      4      5

Required output:
aid      f1      f2 - recent as higher f2 means more recent
2      1      2
1      1      1
6      4      5
5      4      3

SELECT a.aid, a.f1, a.f2
FROM a
WHERE ((((select count(x.f1) from a x where a.f1=x.f1))>1) AND (((select count(x.f1) from a x where a.f1=x.f1 and a.aid>=x.aid))<3))
ORDER BY a.f1, a.f2 DESC;

Open in new window

Output:
aid      f1      f2
2      1      2
1      1      1
6      4      5
5      4      3
0
 

Author Closing Comment

by:CraigMan
ID: 38832074
Just what I needed

Thanks
0
 
LVL 61

Expert Comment

by:mbizup
ID: 38832135
Glad to help :)
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