title: How add unique key to existing table (with non uniques rows)
body: <p>I want to add complex unique key to existing table. Key contains from 4 fields (<code>user_id</code>, <code>game_id</code>, <code>date</code>, <code>time</code>).
  But table have non unique rows.
  I understand that I can remove all duplicate dates and after that add complex key.</p>
  
  <p>Maybe exist another solution without searching all duplicate data. (like add unique ignore etc).</p>
  
  <p>UPD
  I searched, how can remove duplicate mysql rows - i think it's good solution.
  <a href="https://stackoverflow.com/questions/3383898/remove-duplicates-using-only-a-mysql-query">Remove duplicates using only a MySQL query?</a></p>