I just had a look at the ERD of the Wordpress CMS system and I think I found a mistake... Check the relation between the wp_term_taxonomy and the wp_terms table: https://codex.wordpress.org/images/9/9e/WP3.0-ERD.png
If I'm correct ONE wp_term_taxonomy (like "brands") can have more wp_terms (like "puma", "nike" etc.) and not otherwise? Cause it says now that one term can have more taxonomies, am I right?