การตรวจสอบอีเมล์ว่าอีเมล์ที่สมัครสมาชิกนั้นซ้ำกับอีเมล์ของคนอื่นหรือเปล่า

$Email=$_POST['Email'];
$Result=mysql_query("SELECT * FROM tb_member WHERE Email='".$Email."'") or die (mysql_error());
$Num_Rows=mysql_num_rows($Result);

if($Num_Rows==0){
echo "สามารถสมัครได้";
}else{
echo "ไม่สามารถสมัครได้";
}

? 
$username =$_POST["username"];
$password =$_POST["password"];
$email =$_POST["email"];


 $SQL="INSERT INTO users (username,password,email )VALUES ('$_POST[username]','$_POST[password]','$_POST[email]' )";
 

	if(mysql_query($SQL)){
		if (!eregi("^[_a-z0-9-]+(\.[_a-z0-9-]+)*@[a-z0-9-]+(\.[a-z0-9-]+)*(\.[a-z]{2,3})$", $email)){

echo "<script language='javascript'>alert('email ไม่ถูกต้อง');</script>";
echo "<meta http-equiv=\"refresh\" content=\"0;URL=Register.php\" />"; 

		
		
		}else if(mysql_query($SQL)){
		
			echo "<script language='javascript'>alert('สมัครสมาชิกเรียบร้อยแล้วค่ะ');</script>";
			echo "<center> <center><br> <br> <br> <br> <br> <br> <br> <br> <br> <br>";
			echo "<img src='image/loading17.gif'>";
			echo "<meta http-equiv=\"refresh\" content=\"2;URL=Login.php\" />"; 
		exit();
	}
	}


?>

<? 
$username =$_POST["username"];
$password =$_POST["password"];
$email =$_POST["email"];

if (eregi("^[_a-z0-9-]+(\.[_a-z0-9-]+)*@[a-z0-9-]+(\.[a-z0-9-]+)*(\.[a-z]{2,3})$", $email)){
{
     $strSQL  = "SELECT * tb_user WHERE usernaem = '".$username."' ";
     $strSQL .= "AND password = '".$password."' ";
     $strSQL .= "AND email = '".$email."' ";
     $strQuery = mysql_query($strSQL);
     $num_rows = mysql_num_rows($strQuery);
     
     if(!$num_rows)
     {
          $SQL  = "INSERT INTO users (username,password,email) ";
          $SQL .= "VALUES ('$_POST[username]','$_POST[password]','$_POST[email]' )";
          $Query = mysql_query($SQL);
          
          echo "<script language='javascript'>alert('สมัครสมาชิกเรียบร้อยแล้วค่ะ');</script>";
	  echo "<center> <center><br> <br> <br> <br> <br> <br> <br> <br> <br> <br>";
	  echo "<img src='image/loading17.gif'>";
	  echo "<meta http-equiv=\"refresh\" content=\"2;URL=Login.php\" />"; 
	  exit();
     }
     else
     {
          echo "Username หรือ Email มีอยู่ในระบบ แล้ว";
     }
}
else
{
      echo "<script language='javascript'>alert('email ไม่ถูกต้อง');</script>";
      echo "<meta http-equiv=\"refresh\" content=\"0;URL=Register.php\" />"; 
}
?>