>
>
>> I've checked the archives and found an explanation as to how the
>> check if a record is not in a many-to-many table. The answer to that
>> is somewhat simple and clear to me. But here's my problem: how do
>> you check if a record doesn't have a *particular* many-to-many
>> relationship? As in, let's say I have three tables: users, groups,
>> and users_groups linking the two in a many-to-many relationship. Now
>> let's say that I want to select all users who are not in the group
>> "Group1" -- that is, that user may have entries in the users_groups
>> table, but they would be for other groups, not "Group1."
>>
>> One more thing: this is easily done with subqueries, but for
>> performance reasons, I need to do it with explicit joins. Anyone
>> know how I can do this?
>
SELECT u.userID
FROM users u
LEFT JOIN user_groups ug
ON u.userID = ug.userID and ug.groupID = 'Group1'
WHERE ug.groupID IS NULL
