Avoid duplicate entries - duplicates

Question

I have a php code for a sign up form, it stores the details to a table(temp_members_db), then sends a confirmation code to the email entered. If the code is clicked, the details from temp_members_db is transferred to a new table registered_members, from which login details are checked if a user logs in.
The problem is related to the signup code, how can I avoid duplication of emails and username?
My code is:
<?php
include('config.php');
$tbl_name=temp_members_db;
$confirm_code=md5(uniqid(rand()));
$name=$_POST['name'];
$email=$_POST['email'];
$password=$_POST['password'];
$password_confirm=$_POST['password_confirm'];
$sql="INSERT INTO $tbl_name(confirm_code, name, email, password)VALUES('$confirm_code', '$name', '$email', '$password')";
$result=mysql_query($sql);
if
($password != $password_confirm)
{
echo "Password do not match";
}
else if
($result)
{
$to=$email;
$subject="Your confirmation link here";
$header="from: Name <confirm#domain.org>";
$message="Your Comfirmation link \r\n";
$message.="Click on this link to activate your account \r\n";
$message.="http://mydomain#domain.org/confirmation.php?passkey=$confirm_code";
$sentmail = mail($to,$subject,$message,$header);
}
else {
echo "Email not found";
}
if($sentmail){
echo "Your Confirmation link Has Been Sent To Your Email Address.";
}
else {
echo "<BR/>Cannot send Confirmation link to your e-mail address";
}
?>
Thanks :D

Answer 1

Run a SQL to determine if the name or email already exists in any table before INSERT into the database.
You can display error message if the query returns >0.
For example,
SELECT COUNT(*) FROM temp_members_db, registered_members WHERE email = $email OR name = $name;