title: Update nothing on duplicate key exist
body: <p>I'm using the query <code>INSERT INTO ... ON DUPLICATE KEY UPDATE ...</code> in order to insert a record into the table, and if a row with duplicate keys already exists, this results in triggering an update.</p>
  <p>I don't want any updates being performed on an existing row, if exist.</p>
  <p>What should I do to update nothing when a row with duplicate keys exist?</p>