I need to change the meta value of all users at once. Seem there are no api for this,except using custom database query.

This is my code:

```
$matches = array('meta_key' => 'user_token');
$data = array('meta_value' => '100');
$wpdb->update( "$wpdb->usermeta", $data, $matches);

```

The problem is this only update one user meta value, not all users meta value with the meta key of 'user\_token'.  

Does $wpdb->update limited to update single row only? Or I did something wrong?