PHP SQL select where in array of IDs and has same variable column value [duplicate]

Answer 1

SELECT group_id 
FROM group_user 
WHERE user_id IN (9,7,6) 
GROUP BY group_id
HAVING count(DISTINCT user_id) = 3
AND count(DISTINCT group_id) = 1

makes sure that all 3 ids are in the same group_id and that they're not in any other group.

http://sqlfiddle.com/#!9/540f96/2

Answer 2

You can use conditional aggregation to find group_id's which have the required user_id's associated with them.

SELECT group_id 
FROM group_user 
group by group_id
having sum(case when user_id IN (9,7,6) then 1 else 0 end) = 3

Answer 3

Your query should be:

SELECT DISTINCT(group_id) FROM group_user WHERE user_id IN (9,7,6)