To see how many elements a mysql result has in php you use mysql_num_rows like so:
 
$query="select * from news where a=1 order by id desc";$result=mysql_query($query);if (mysql_num_rows ($result) == 0){  echo 'no news has been added yet'
}
else {  while($row=mysql_fetch_array($result))    {
       ......
    }}