What site would you recommend for creating categories and subcategories in SQL?

Question

SQL

I'm pretty good with relational databases in access (creating schemas and relationships in visual mode), but I don't understand how it works in SQL.

Answer 1

hmm...i don't understand the question.
entity_id - INT
category_entity_id - int (link to table_category.entity_id)
entity_id - INT
parent_id - INT // parent id
category_name - varchar
So, no?

Answer 2

Maybe so, but in this diagram they are also considered as subcategories?
It's just that I think I'm making it harder for myself by trying to do it via CONSTRAINT like in the example below:

CREATE TABLE my_subcat_2(
   id_subcat_2 NUMBER
 , subcat_2_name VARCHAR2(100) NOT NULL
 , CONSTRAINT my_subcat_2#p
      PRIMARY KEY(id_subcat_2)
 , CONSTRAINT my_subcat_2#R#my_master
      FOREIGN KEY(id_subcat_2)
      REFERENCES my_master(id_master)      
   )
;