Question

Suppose I have a table like this:

| uid | group_id | 
-----------------
|   1 |     1    |
|   1 |     2    |
|   1 |     3    |
|   1 |     4    |
|   2 |     1    |
|   2 |     2    |
|   2 |     3    |
|   3 |     1    |
|   3 |     2    |
|   3 |     4    |
...

How can I get the common set of group_ids for some set of uids.

For e.g.
for uid 1,2 : The common group_ids are 1,2,3
for uid 1,2,3 : The common group_ids are 1 and 2

Answer 1

Assuming each group_ID is unique for every uid, (otherwise you need to use distinct)

SELECT group_ID
FROM tableName
WHERE uid IN (1,2,3)
GROUP BY group_ID
HAVING COUNT(*) = 3

• SQLFiddle Demo (includes two queries)