جلوگیری از ورود رکورد تکراری (PHP-MySQL)

سلام
خب خیلی سادست!
Select بگیر از رکوردی وجود داشت insert نکن!

<?php
    if(isset($_POST['submit']))
    {

    //get the name and comment entered by user
    $firstName = $_POST['firstName'];
    $lastName = $_POST['lastName'];

    //connect to the database
    $dbc = mysqli_connect('host', 'username', 'password', 'dbname') or die('Error connecting to MySQL server');
    $check=mysqli_query($dbc,"select * from clients where firstname='$firstname' and lastname='$lastname'");
    $checkrows=mysqli_num_rows($check);
   if($checkrows>0){echo "customer exists";}  
else{  
    //insert results from the form input
    $query = "INSERT IGNORE INTO clients(firstName, lastName) VALUES('$firstName', '$lastName')";

    $result = mysqli_query($dbc, $query) or die('Error querying database.');

    mysqli_close($dbc);
    }
    echo "Customer Added";};
    ?>

راه دیگش اینه که از INSERT IGNORE استفاده کنی