cannot add data to tables!! please help!

I cannot get data added to my plugin tables from a form. I’ve tried just about everything. I am able to submit the data but nothing happens and I get no errors or anything. The values are the same as the form input type
names.
Here’s the code:
<?php
global $wpdb;

if(isset($_POST[‘submit’])){

if ($wpdb->query(“INSERT INTO ".$wpdb->prefix."release_table ( artist_name , title , release_date , label_id , format , buy_url , ‘info’ ) VALUES ( ‘”.artist_name.”‘, ‘”.title.”‘, ‘”.release_date.”‘, ‘”.label_id.”‘, ‘”.format.”‘, ‘”.buy_url.”‘, ‘”.format.”‘ );”)) {
echo “<p align=’center’>”.TXT_WPSC_COUPONHASBEENADDED.”</p>”;
include_once(‘wp-config.php’);
include_once(‘wp-includes/wp-db.php’);

}
}

?>