rporter45
asked on
Access 2007 - How do I count unique ID's
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.
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.
GRayL
SELECT AccountID, Count(ContactID) as CountOfContacts FROM myTable GROUP BY AccountID;
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ASKER
This one provided the exact syntax.
Oops:
SELECT a.AccountID Count(a.ContactID) AS CountUniqContacts FROM (
SELECT DistinctROW AccountID, ContactID FROM myTable) AS a GROUP BY a.AccountID;
SELECT a.AccountID Count(a.ContactID) AS CountUniqContacts FROM (
SELECT DistinctROW AccountID, ContactID FROM myTable) AS a GROUP BY a.AccountID;
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]
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]
I believe you selected answer will count multiple ContactID's.
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.