If you are ever in need of finding duplicates in a mysql field but dont want to open phpmyadmin you can simply do this.

PHP Code:
("localhost""username""password") or die(mysql_error());
mysql_select_db("dbname") or die(mysql_error());

$result mysql_query("select field, count(field) as cnt
        from table
        group by field
        having cnt > 1
        order by cnt; "

    or die(
$row mysql_fetch_array$result )) 
This will return any duplicates, but only 1 result of the dup.

Of course change table and field in the snippet to your own.