title: MySQL: delete duplicate rows, keep none
body: <p>newbie here, for this table I would like to remove all ID's (rows) that don't have a unique number in Event. So far I found only solutions that will keep one ID, but remove the duplicates.</p>
  
  <pre><code>    +-----------+--------------+----------+--------+
      | ID        | Costs        |   Date   | Event  |
      +-----------+--------------+----------+--------+
      |     1     |      100     |2012/09/10|  5     |
      +-----------+--------------+----------+--------+
      |     2     |      300     |2012/09/20|  5     |
      +-----------+--------------+----------+--------+
      |     3     |      400     |2012/10/01|  4     |
      +-----------+--------------+----------+--------+
  </code></pre>
  
  <p>I have tried the <code>ALTER IGNORE TABLE ADD UNIQUE INDEX</code> function, but i don't want to keep one ID. For example, in this table I would like to remove the rows from ID 1 and 2, but keep ID 3. </p>
  
  <p>Note: all ID's are unique.</p>
  
  <p>Thank you.</p>