how do i use join in php mysql i dont undertand the problem

[kayman]

<?php

require 'datacon.php';
$staffid ='asd';
$query="SELECT lecturers.staffid, tutors.staffid FROM lecturers , tutors WHERE lecturers.staffid = '".$staffid."', tutors.staffid = '".$staffid."' ";

if($result = mysql_query($query) ){

while($row = mysql_fetch_array($result)){
echo $row['staffid'];
echo "<br />";
}
}else if($result==''){

echo 'the query is empty';
}else{
echo die(mysql_error().'there was a failure');

}


?>

and this is the output

the query is empty