WooCommerce Attribute Taxonomies List?

I am trying to create an array with the WooCommerce Attribute Taxonomies, I have found the values in a database custom table, I have the code below, but the variable $attrib_info is empty!

global $wpdb,$table_prefix;
$post_sql = "select * from $wpdb->woocommerce_attribute_taxonomies";
$attrib_info = $wpdb->get_results($post_sql);

Is there another function to return the list of ‘pa_’ single term values not the siblings or from the post meta, just the top level.

if we are looking at the dummy data I would only get color and capacity returned.

Any help appreciated.

David