title: MySQL combine groups within a single table
body: <p>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:</p>
  
  <pre><code>user      region     field1
  ----      ------     ------
  282       10         38
  282       10         128
  464       3          57
  </code></pre>
  
  <p>etc.</p>
  
  <p>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"</p>
  
  <p>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'?</p>