ใช้ฟังก์ชั่น datediff แร้วเกิด error ในการลบข้อมูลเมื่อวันที่ตรงกับวันหมดอายุ

$sql4= "DELETE FROM receive WHERE DATEDIFF(Date_Expire<NOW())"; 
mysql_query($sql4) or die(mysql_error());

//ลบข้อมูลเมื่อถึงกำหนด     
	$sql3="SELECT * FROM  receive WHERE DATEDIFF(NOW(),Date_Expire)=0";
	$result3=mysql_query($sql3);
	while($row = mysql_fetch_array($result3)){	
	    $ID	= $row[DonorID];
		$Bag = $row[BagNumber];
		$Blood = $row[BloodG];
    	$Date_do = $row[Date_Donation];
		$Type = $row[Type];	
		$Quan = $row[Quan];
	}	
	echo "คัยหมดอายุ". $ID;
    $Status ="หมดอายุ"; 
   //if($Date_ex == $var){
  $result4 = mysql_query("Insert Into deleteblood (DonorID,BagNumber,BloodG,Date_Donation,Date_Delete,Type,Quan,Status) VALUES('$ID','$Bag','$Blood','$Date_do','$var','$Type','$Quan','$Status')");
   //}
   if($Date_ex == $var){
   $result2 = mysql_query("DELETE FROM receive WHERE Date_Expire='$var'");
   $dbQuery = mysql_query($result2) or die ("Error Query :".$result2."");
   echo $delex;
   }

   $result2 = "DELETE FROM receive WHERE Date_Expire='$var'";
   $dbQuery = mysql_query($result2) or die ("Error Query :".$result2."");