I need to make database model about libraries. In that model I'm tracking more libraries and every library has it's own moderators. Every moderator can make categories of the books and than add books in categories (note: another library doesnt need to have same as categories of books as library where that moderator is working, every other library can have different categories of books .. ).
This picture represents how did I make it. But something is missing, think this is not good solution. I have also another tought.. To link tables "book" and "category_book" in N:M and than link "book" and "libraries" which from I can get everything I need. But, think it's also not the best solution because every library will in that moment has same categories of books.
Am I missing something or? Haven't met with this kind of problem yet so if you could help me I will be grateful