multisite prefixes

[Angeloverona]

since WordPress is multiblog site, we have still only one prefix function like "wpdb->prefix;" for now we have many blogs with unique prefixes... in modules we can easily use this "wpdb->prefix; to get unique prefix of active site...but how can we get a primary prefix for main blog in modules? i have funtion like:

substr($wpdb->prefix, 0, stripos($wpdb->prefix, "_")+1);

but this can be used only if prefix look like as "cars_", if someone use prefix like "my_cars_" this method will fail.

it will be good to enhance this prefixes like get prefix by id, or more simply get base prefix.
$wpdb[0]->prefix,$wpdb->prefix_id,$wpdb->base_prefix

[Angeloverona]

don't use this $wpdb[0]->prefix :)

[Angeloverona]

add "base prefix" to db table(_site) or to (_blogs) table prefix column for all blogs

[nacin]

$wpdb->get_blog_prefix( $blog_id );