For example there can be two duplicates with id 5, and 200 and obviously 200 is most up-to-date, but when you execute your SQL 200 will be removed and 5 will stay.

1)
{
$x = 1;
while($x <= $i)// we loop inside the loop – this can mean quite a lot of operations so think carefully about the limit above
{
if($entry[$i] == $entry[$x])// checking string against previous entries
{
$delete_duplicate = mysql_query(“DELETE FROM `table_name` WHERE `id`=’”.$id['id'].”‘”); //delete duplicate
/*
or if wish to check first then add another field in the table (e.g. `check`) and change query into
something like this:
$mark_duplicate = mysql_query(“UPDATE `table_name` SET `check`=’1′”);
then if happy run something lie this:
$delete = mysql_query(“DELETE FROM `table_name` WHERE `check`=’1′”)
*/
echo ‘Entry #’.$id[$i].’ was the same as entry ‘.$id[$x].’ and has been deleted.’;
}
$x++;
}
}
$i++;
}
?>

ALTER IGNORE TABLE dupTest ADD UNIQUE INDEX(a,b);

lovely jublee
thank you