title: What's the SQL query to list all rows that have 2 column sub-rows as duplicates?
body: <p>I have a table that has redundant data and I'm trying to identify all rows that have duplicate sub-rows (for lack of a better word). By sub-rows I mean considering <code>COL1</code> and <code>COL2</code> only. </p>
  
  <p>So let's say I have something like this:</p>
  
  <pre><code> COL1   COL2   COL3
   ---------------------
   aa     111    blah_x
   aa     111    blah_j
   aa     112    blah_m
   ab     111    blah_s
   bb     112    blah_d
   bb     112    blah_d
   cc     112    blah_w
   cc     113    blah_p
  </code></pre>
  
  <p>I need a SQL query that returns this:</p>
  
  <pre><code> COL1   COL2   COL3
   ---------------------
   aa     111    blah_x
   aa     111    blah_j
   bb     112    blah_d
   bb     112    blah_d
  </code></pre>