Omit repeated values in mysql query so the json file has only one of each

This is the query part of my json.php which is the source file of my jquery ui autocomplete input

$term = trim(strip_tags($_GET['term']));//retrieve the search term that autocomplete sends



$qstring = "SELECT nombre as value FROM ingredientes WHERE nombre LIKE '%".$term."%'";

$result = mysql_query($qstring);//query the database for entries containing the term



while ($row = mysql_fetch_array($result,MYSQL_ASSOC))//loop through the retrieved values

{

    $row['value']=htmlentities(stripslashes($row['value']));

    //$row['id']=(int)$row['id'];

    $row_set[] = $row;//build an array

}

echo json_encode($row_set);//format the array into json data

The problem is that file my return result as:

[{"value":"one"},{"value":"one"},{"value":"ones"},{"value":"ona"}]

So the word will be suggested twice. How can I prevent that?