Question

I am simply trying to query a table to return a boolean value, which seems to only ever return null.

$sTable4 consists of the columns userid & artistid

$artistid is a parameter passed in to the script (which is definitely being correctly passed)

$userid is the id of the currently logged in user.

User are able to save artists in to their favourites list.

What I want is to check this table for the currently logged in user and a specific artistid which is declared in the variable above to see if an entry exists. If it doesn’t then I want it to return null and to return ‘1’ if it does.

Any ideas where I am going wrong?

SELECT userid, artistid
FROM $sTable4 AS b
WHERE NOT EXISTS
(
   SELECT artistid
   FROM $sTable4 AS ab
   WHERE b.userid = $userid
      AND b.artistid = $artistid
)

Answer 1

Nothing going wrong, Actually you are trying to select userid, artistid from $sTable4 where they are not exists in the same table, so what do you expect and how would you select them if they are not exists?!! I think you are missing something in your query, becouse this check will always return null as they are exists, so it won’t select them. So i think where exists will work for you like this:

SELECT ab.artistid
FROM $sTable4 AS ab
WHERE exists 
(
    select artistid 
    from $sTable4 b 
    where b.userid=$userid AND b.artistid=$artistid
)