จะทำ textbox เป็นตัวรับค่าเพื่อตรวจสอบเรคอสที่จะแก้ไข แต่ไม่รู้ทำไง ช่วยด้วยคับ

<form name="myfrm" action="" method="get">
	ID:&nbsp;<input type="text" name="Txt_Id" id="Txt_Id" />
</form>

<?php
	if($_GET["Txt_Id"] == ""){
		echo "<h2>Result Here.</h2>";	
	}else{
//*** Connct database to show record. ***//
	$Connect = mysql_connect("localhost", "username", "password") or die (mysql_error());	
	$SelectDB = mysql_select_db($Connect);
if(!$SelectDB){
	echo "Can't select databases.";	
}else{
	$tablename = "";
	$Sql = "SELECT * FROM $tablename";
	$Qr_Sql = mysql_query($Sql) or die (mysql_error());
	while($fetch_Sql = mysql_fetch_array($Qr_Sql)){
		//*** Show record from databases ***//	
	}
		
	}
}
?>