title: T-SQL difference between WHERE EXISTS and INTERSECT
body: <p>Can you tell me what is the difference between these two? 
  I have tried using both for comparing two tables, but the results are a bit different:</p>
  
  <pre><code>  SELECT a.CustID FROM tbl1 AS a 
    WHERE EXISTS (SELECT b.CustID FROM tbl2 b WHERE (a.CustID=b.CustID))
  </code></pre>
  
  <p>This query results 178 rows. However, the query below results in 162 rows.</p>
  
  <pre><code>  SELECT a.CustID FROM tbl1 AS a
    INTERSECT
    SELECT b.CustID FROM tbl2 AS b
  </code></pre>