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Access 2007 - How do I count unique ID's

Posted on 2010-09-19
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Last Modified: 2012-05-10
I have a table with two columns of data.

Account ID
Contact ID

Please provide me with the SQL statement to use in Access 2007 to output a new table where each account ID appears only once and in the second column there is a column indicating the number of unique contact ID's for each account.
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Question by:rporter45
7 Comments
 
LVL 44

Expert Comment

by:GRayL
ID: 33712437
SELECT AccountID, Count(ContactID) as CountOfContacts FROM myTable GROUP BY AccountID;
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Accepted Solution

by:
Rey Obrero (Capricorn1) earned 2000 total points
ID: 33712440
select [Account ID], count([contact ID])
from tablex
group by [account ID]
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Author Closing Comment

by:rporter45
ID: 33712451
This one provided the exact syntax.
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LVL 44

Expert Comment

by:GRayL
ID: 33712453
Oops:

SELECT a.AccountID Count(a.ContactID) AS CountUniqContacts FROM (
SELECT DistinctROW AccountID, ContactID FROM myTable) AS a GROUP BY a.AccountID;
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LVL 49

Expert Comment

by:Dale Fye
ID: 33712457
Well, if your current structure allows you to have multiple records with the same accountID and ContactID, then neither of the above will work.  You will first need to get DISTINCT combinations of AccountID and ContactID, so try:

SELECT T.[Account ID], Count(T.[Contact ID]) as UniqueContacts
FROM (SELECT DISTINCT [Account ID], [Contact ID] FROM your Table) as T
GROUP  BY T.[Account ID]
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LVL 44

Expert Comment

by:GRayL
ID: 33712458
I believe you selected answer will count multiple ContactID's.
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LVL 44

Expert Comment

by:GRayL
ID: 33719434
I have run tests and fyed's solution at http:#a33712457 is correct.  My solution in the previous post is not correct as I used DISTINCTROW instead of DISTINCT.
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