Question

I am trying to write syntax that checks for group membership based on a single table. I have users that are in the table multiple times (meaning, multiple rows), so I might have data that looks like this:

user      region     field1
----      ------     ------
282       10         38
282       10         128
464       3          57

etc.

What I need is syntax that says “Group A = Region 10 and ANY of these numbers in the FIELD1 column – 38, 79, 126. Then Group B = Region 10 and ANY of these numbers in the FIELD1 column – 80,128”

Now, as you can see from my example, user 282 would be considered in BOTH Group A and Group B. Ultimately, I’m looking to find out who is in both groups. I did a GROUP_CONCAT to show me that they’re in the same group but how do I count them or even filter on the ‘Groups’?

Answer 1

Use a self-join:

SELECT DISTINCT t1.user
FROM MyTable t1
JOIN MyTable t2 USING (user)
WHERE t1.region = 10 AND t1.field1 IN (38, 79, 126)
AND t2.region = 10 AND t2.field1 IN (80, 126)