title: sql help to find out multiple entries
body: <p>I have a table <code>t1</code> with the values </p>
  
  <pre><code>col1 col2 
  1     2
  1     4
  1     4
  2     4
  2     4
  3     5
  3     5
  4     3
  4     3
  5     1
  5     1
  5     6
  5     6
  </code></pre>
  
  <p>I need to get the output as </p>
  
  <pre><code>1     2
  1     4
  5     1 
  5     6
  </code></pre>
  
  <p>That is when <code>col2</code> has multiple entries I am interested in those records only. </p>
  
  <p>Any help?</p>