title: Delete duplicate entries via SQL?
body: <p>Is there any possibility in SQL to remove (only one) duplicate entries of composed columns (here: city, zip)?  So if i have this SQL:</p>
  
  <pre><code>INSERT INTO foo (id, city, zip) VALUES (1, 'New York', '00000')
  INSERT INTO foo (id, city, zip) VALUES (2, 'New York', '00000')
  </code></pre>
  
  <p>Can i remove the first later with a sql statement? My approach doesn't work for that</p>
  
  <pre><code>DELETE FROM foo (id, city, zip) 
         WHERE id IN 
               (SELECT id FROM foo GROUP BY id HAVING (COUNT(zip) &gt; 1))
  </code></pre>