CODEWITHSUNDEEP
sqlsql-serversql-server-2008t-sql
Ragnar
Ragnar

Reputation: 1582

Select ID Where only one value exists for that ID

I have a table with a UserID and ImageID Column. I want to select all the UserId's with only one ImageID. I have the code below.

Select UserID From AF.UserImageTable
Where Count(ImageId) = 1

When I run the code I get the error. 

An aggregate may not appear in the WHERE clause unless it is in a subquery contained in a HAVING clause or a select list, and the column being aggregated is an outer reference.

The table looks like this

_________________________
: ImageID    :   UserID :
: 12345      :   10002  :
: 56789      :   10002  :
: 29292      :   10002  :
: 12345      :   10001  :
: 56789      :   10001  :
: 56789      :   10003  :
________________________

If I run the Query on the table above I'm trying to get it to return 10003

Upvotes: 3

Views: 2413

Answers (4)

Xenophage
Xenophage

Reputation: 85

I see you have several ImageID's shared by multiple UserID's, is this only for example or do you also need to exclude these cases? If you want to get out of grouping limitations, you could also try a sub query. You can get all data from your table, and can easily change if you want to view people with one image only, or two images only, etc...

SELECT AF.ImageID, AF.UserID
FROM UserImageTable AF
WHERE AF.UserID IN (
SELECT AF2.UserID
FROM UserImageTable AF2
GROUP BY UserID 
HAVING COUNT(AF2.ImageId) = 1--Switch to 2 or 3 for more images.
)

Upvotes: 0

irakliG.
irakliG.

Reputation: 176

If you also need to get [ImageID] values there is query:

SELECT UserID, max(ImageID) as ImageID
FROM AF.UserImageTable
GROUP BY UserID 
HAVING COUNT(ImageId) = 1

Upvotes: 1

cableload
cableload

Reputation: 4375

When you use the below group by clause with the HAVING clause, the GROUP BY clause divides the rows into sets of grouped rows(in this case UserID and aggregates their values) and then the HAVING clause eliminates groups that you dont need.

Select UserID,count(ImageId) From AF.UserImageTable
group by UserID having Count(ImageId) = 1

Upvotes: 4

Adam Silenko
Adam Silenko

Reputation: 3108

try :

Select UserID 
From AF.UserImageTable
Group By UserID 
Having Count(ImageId) = 1

Upvotes: 1

Related Questions