Update WP user_login via SQL

gistfile1.php

<?php

// Force update our username (user_login)
global $wpdb;
$tablename = $wpdb->prefix . "users";
	
// method 1
//$sql = $wpdb->prepare("UPDATE %s SET user_login=%s WHERE ID=%d", $tablename, $user_email, $user_id);
//$wpdb->query($sql);
    
// method 2
$wpdb->update( $tablename, array( 'user_login' => $user_email ), array( 'ID' => $user_id ) );

?>