Is there any solution about this hierarchical structure of data model in SQL?

Question

I have this data model. This data model is about e-shop structure by categories.

item_category - every subcategory on website. item - every item on e-shop (item_category_id - every subcategory on website (leaf)).

parent_id is self-referent and define the hierarchical structure. Roots of hierarchical structure mean main categories.

item_category_transitive_closure - it is a redundant data structure containing a transitive closure of the supercategory-subcategory relation, which is represented by the self-reference parent binding above the item_category table

• Every representation of a link between two categories is meaningful
• lies on the path to the root of the categories tree from the given category (#sub_cat_id) 0, M: 0, M
• which are descendants of the category (#super_cat_id) within the category tree (0,M: 0,M)

Target is "Count of items by main categories" in SQL.

Thank you for your help

Answer 1

if you look at this link Get Root Node it should show you how to get the root (main) category for any category ID in your item_category hierarchy table. Just join this result set to whatever query you write to be able to include the Main Category in it