แสดงข้อมูล จากการจอยตารางยังไงครับ ไม่รู้ว่าใช้คำสั่งถูกด้วยไหม ช่วยดูให้ทีครับ

if($id_tech!=""){
		$sql = "SELECT tbl_tech.*,tbl_name.*,tbl_agen.*,tbl_type.* FROM tbl_tech,tbl_name,tbl_agen,tbl_type WHERE tbl_name.id_name = tbl_tech.id_name,tbl_agen.id_agen = tbl_tech.id_agen,tbl_type.id_type = tbl_tech.id_type order by id_type1 limit $goto,$list_page"; 
		}else $sql = "SELECT tbl_tech.*,tbl_name.*,tbl_agen.*,tbl_type.* FROM tbl_tech,tbl_name,tbl_agen,tbl_type WHERE tbl_name.id_name = tbl_tech.id_name,tbl_agen.id_agen = tbl_tech.id_agen,tbl_type.id_type = tbl_tech.id_type limit $goto,$list_page"; 
//$sql = "select * from tbl_tech order by catalog desc limit $goto,$list_page";
$dbquery = mysql_db_query($dbname, $sql);
//$n=$NRow+1;
while ($result = mysql_fetch_array($dbquery))      //บรรทัดนี้มัน error น่ะครับ 
{
    //$id_tech = $result[id_tech];
	$tech_detail = $result[tech_detail];
	$names = $result[names];
	$agen = $result[agen];
	$tel = $result[tel];
	$tech_charge = $result[tech_charge ];
	$types = $result[types];
	$tech_pdf = $result[tech_pdf];
	$show_pdf = "../pdf/res/$tech_pdf";