title: Selecting all duplicates from table
body: <p>I'v got a table with columns like this:</p>
  
  <pre><code>serial_id   season  ep_id
  1           1       1   &lt; duplicate
  1           1       2
  3           1       1
  ...
  1           1       1   &lt; duplicate
  </code></pre>
  
  <p>I want to select all rows that have a duplicated values in serial_id, season and ep_id , what query i should use?
  Thanks.</p>