อยากทราบเงื่อนไขในการเขียนค้นห้าข้อมูลครับยังติดปัญหานิดหน่อยช่วยรบกวนดูให้ทีน่ะครับ

$type=$_POST['type'];
$province=$_POST['province'];




if($_POST['type'] == '0' or $_POST['province']== '0' ){
$sql = " SELECT * FROM tbl_position ";	
}else if($_POST['type'] == $type or $_POST['province'] == $province ){
$sql =  "SELECT * from tbl_position WHERE (com_type ='$type' or com_place ='$province'  )";
}

$type=$_POST['type'];
$province=$_POST['province'];


if($_POST['type'] == '0' or $_POST['province']== '0' ) // empty keyword
{
$sql = " SELECT * FROM tbl_position ";	
}
else if($_POST['type'] != "0" and $_POST['province'] !="0") // 2 keyword
{
$sql =  "SELECT * from tbl_position WHERE (com_type ='$type' or com_place ='$province'  )";
}
else if($_POST['type'] != "0" and $_POST['province'] =="0") // 1 keyword type
{
$sql =  "SELECT * from tbl_position WHERE com_type ='$type'";
}
else if($_POST['type'] == "0" and $_POST['province'] !="0") // 1 keyword province
{
$sql =  "SELECT * from tbl_position WHERE com_place ='$province'";
}