รบกวนขอตัวอย่าง คำแนะนำการ join กัน 7 ตารางทีค่ะ มีใครเคยทำบ้างมั้ยคะ

$str = "select  qc_record.*,standardvalue.*,inspection_rec.*,ball_model.Balltype,country.Country,artwork.Rev,employee.*";

$str.="from qc_record LEFT JOIN standardvalue ON (qc_record.Po=standardvalue.Po)"
 $str.=      " LEFT JOIN standardvalue ON (qc_record.Po = standardvalue.Po)"
 $str.=     "LEFT JOIN inspection_rec ON (qc_record.Po=inspection_rec.Po)"
 $str.=     "LEFT JOIN ball_model ON (qc_record.ModelID=bal_modell.ModelID)"
$str.=      "LEFT JOIN country ON (qc_record.CountryID=country.CountryID)"
$str.=      "LEFT JOIN artwork ON (qc_record.Artwork=artwork.Artwork )"
 $str.=      " LEFT JOIN employee ON (qc_record.EmpID=employee.Artwork.EmpID )"