Question

I have a table like so :

| thread_id | user_id |
+-----------+---------+
|     1     |    1    |
|     1     |    2    |
|     2     |    1    |
|     2     |    3    |
|     3     |    1    |
|     3     |    3    |
|     3     |    2    |
           ...

How would I check if an array combination exists and belongs to the same thread ?

Ex:

1,3     => return true
3,1,2   => return true
1,4,2,3 => return false

Arrays could contain several hundred id’s, with hundreds of thounds of threads.

Answer 1

SELECT NULL
WHERE  EXISTS (
           SELECT   NULL
           FROM     your_table
           WHERE    user_id IN (1,2,3,4,..., ...)
           GROUP BY thread_id
           HAVING   COUNT(*) = n
       )

Where n is the count of items in the list / array.

Then in your script:

• If a row was returned: true
• Else: false