title: how can I delete double entries of different column
body: <p>with other form i have table like</p>
  
  <pre><code>rowsid     source_row   same_as_row 
  
  row1       1                18    
  
  row2       3                 18
  
  row3       18                1
  
  row4       18                3
  </code></pre>
  
  <p>i want only elimate  the rows3 and row4 :</p>
  
  <pre><code>row3       18                1
  
  row4       18                3
  </code></pre>
  
  <p>which query! to delete query row3 and row4 .help</p>