title: Mysql delete older duplicates
body: <p>I've got table with this data</p>
  
  <p>id, archive id, ean, index, date, (...)</p>
  
  <p>I've got some items with same archive id, same ean, but different index.</p>
  
  <p>So in this case, I want to delete older (basing on date) item, so result will be that for each combination archive_id/index there will be no more than 1 result.</p>