How can I model this class in a database?

Question

I need a little of help. This is my design to organize several categories.

   Category 1
     Sub Category 1.1
       Sub Category 1.1.1
     Sub Category 1.         


        

Answer 1

You'd have a table something like this:

• category
  • id (primary key, not null)
  • name (text, not null)
  • parent_category_id (foreign key to category.id, nullable)

Then, if a category has a parent, you reference the id of that other row. So the table is self-referential. Toplevel categories have a null parent_category_id.

When building tables like this you do need to be careful that you don't create a circular reference.