รับค่าจาก Text Field มาเปรียบเทียบกับค่าที่อยู่ในฐานข้อมูลทำอย่างไรครับ

<?
	session_start();
	
	$borrowdated=$_POST["datewantd"];
	$datewant=$_POST["datewant"];
	$checkidbring[]=$_POST["checkidbring"];
	echo "count = ".count($checkidbring)."<br>";
	for($i=0; $i<(count($checkidbring)-1); $i++)
	{
		$number=$_POST["number".$checkidbring[$i]];
		$_SESSION["number".$checkidbring[$i]] = $number;
		echo "checkidbring $i = ".$checkidbring[$i]."<br>";
		
		include "connect.php";
		$sql3="select * from tb_rentwant WHERE status='1' order by idrentwant='$checkidbring[$i]'";
		$result3=mysql_db_query($dbname,$sql3);
		//$num_row3= mysql_num_rows($result3);
		$arr3 = mysql_fetch_array($result3);
		$idbring= $arr3[idrentwant];
		$rentdat = $arr3[rentdated];
				$date1 =(int)$datewant-(int)$rentdat ;
				if($date1<0)
					{			
						echo"มีผู้เช่าก่อนหน้านี้แล้วกรุณาตรวจสอบวันที่ส่งคืนอีกครั้งครับ";
						print "<meta http-equiv=refresh content=2;URL=assrent.php>"; exit() ;
						$result = mysql_query($sql);
					}
		
		else{
		$sql="select * from tb_rent WHERE idrent='$checkidbring[$i]'" ;
		
		include "connect.php";
		$sql="select * from tb_rent WHERE idrent='$checkidbring[$i]'";
		$result=mysql_db_query($dbname,$sql);
		$num_row= mysql_num_rows($result);
		$num_fields= mysql_num_fields($result);
		
		echo "numrow = " .$num_row;
		
		$arr = mysql_fetch_array($result);
		$idbring= $arr[idrent];
		$name = $arr[name];
		$detail = $arr[detail];
		$amount = $arr[amount];
		$unit = $arr[unit];
		$status = $arr[status];
		
		$temp =(int)$amount-(int)$number ;
		$tempmaterialID= $checkidbring[$i];
		
		if($temp>=0)
		{			
			$sql2= "INSERT  INTO  tb_rentwant  (idrentwant, amountwant,rentproject,rentusername,rentdate,rentdated)VALUES('$checkidbring[$i]','$number','$project','$sess_username','$datewant','$borrowdated')";
			echo "$sql2 <br>";
			$result2 = mysql_query($sql2);
		}
		}
	}
	session_register("checkidbring");
	header("location:assrent2.php");

?>