local-config.php

<?php
define('DB_NAME', 'LOCAL_DB_NAME');

/** MySQL database username */
define('DB_USER', 'LOCAL_DB_USERNAME');

/** MySQL database password */
define('DB_PASSWORD', 'LOCAL_DB_PASSWORD');

/** MySQL hostname */
define('DB_HOST', 'localhost');
?>

wp-config.php

if (file_exists(dirname(__FILE__).'/local-config.php')) {
    include( dirname(__FILE__).'/local-config.php');
}
else {
    define('DB_NAME', 'SERVER_DB');

    /** MySQL database username */
    define('DB_USER', 'SERVER_DB_USER');

    /** MySQL database password */
    define('DB_PASSWORD', 'SERVER_DB_PASSWORD');

    /** MySQL hostname */
    define('DB_HOST', 'localhost');
}