title: (SQL) Replaced NOT IN with NOT EXISTS and results differ
body: <p>Trying to fix someone else's code. The NOT IN kills performance.
  I took it  out and replaced with Not Exists and I'm getting different results.
  The commented out not in is just above my not exists. 
  Anyone see anything stupid I'm doing here?</p>
  
  <pre><code>IF @ProcessComplete = 1
      BEGIN
  
  --      PRINT 'Group-Complete'
      INSERT INTO @ProcessIDTable
      SELECT DISTINCT(ProcessID)
      FROM vPortalInbox
      WHERE  GroupUserIDs LIKE '%,' + CAST(@UserID AS VARCHAR(MAX)) + ',%' 
      AND StepOwnerID IS NULL
  
      --AND ProcessID NOT IN (SELECT ProcessID FROM @ProcessIDTable)
  
      And  not exists (SELECT ProcessID FROM @ProcessIDTable)
  </code></pre>