title: How to merge 2 mysql databases with same structure and common entries
body: <p>I am not sure that there is a simple solution to my problem but ...</p>
  
  <p>I dumped a mysql database from a production machine to run migration tests on a test machine. 
  Tests went well so 2 days later I did the migration on the production machine after dumping the database again (for safety). </p>
  
  <p>There was a problem during migration and the database was corrupted so I had to restore the dumped database. The second migration attempt went OK.</p>
  
  <p>Now here is the thing : I realised a few days later that I made a mistake and restored not the dump I made just before the migration but the first one I made 2 days ago for testing purpose. </p>
  
  <p>I know, I suck, I hate myself today ...</p>
  
  <p>I now have this to try something :</p>
  
  <ul>
  <li><p>the first dump (but I don't think it is useful)</p></li>
  <li><p>the second dump which was the one I should have restored but didn't</p></li>
  <li><p>the current database with a 2 day gap, it contains data of the first dump plus a few days of new entries from after the restoration.</p></li>
  </ul>
  
  <p>I wish to merge these databases so I end up with one which contains everything. </p>
  
  <p>Since the second dump and the current database have most entries in common I have to ignore duplicate but the ignore option (if I understand well) is based on primary keys and it would also ignore some new entries because they have the same primary keys than the one from the 2 day gap. So I am stuck with my own little knowledge.</p>
  
  <p>I am not a specialist of mysql so I hope someone here can help me with that.</p>
  
  <p>Is there a way to merge the databases in a way that only real duplicates (entire row is identical) are ignored ?</p>