Question

I have a table as follows

id comm_id user_id ..

This stores user subscriptions to communities. Now I want to query this table so that only those subscriptions are fetched which are mutual between 2 users(say user_id: 2 and 9)

Give me the sql query
tablename: db_community_subscribers
id, community_id, user_id

"20"      1         "2"
"28",  NULL         "2"
"31"   NULL,        "2"
"43",   4           "2"
"47     1             9
"57",   NULL,       "2"
"59",   "12",      "9"
"60     14          2
"62",  NULL         2

These are the subscriptions of users 2 and 9

I want to select only 1 and 12 since these are the common subscriptions

Answer 1

try this one:

I think this will work now:

SELECT Comm_ID
FROM tableNAme
WHERE  user_id IN (2,9)
GROUP BY Comm_ID
HAVING COUNT(Comm_ID) > 1

OR

SELECT DISTINCT d.Comm_ID
FROM
    (SELECT Comm_ID
    FROM tableNAme
    WHERE user_id in (1,2)) d
GROUP BY d.Comm_ID
HAVING COUNT(d.Comm_ID) > 1