how to store a catalog like this?
I want to have a book table (book table, book title, introduction, cover, etc.)
articleOne association table (book and article id association table, book id, first-level article catalogue id)
articleTwo association table (first-level article catalogue and second-level article catalog id, first-level article catalog id)
check articleOne table first. Find out the first-level article directory id, and then according to the first-level article directory id to check the articleTwo table, find out the second-level article directory id, and then find out the article title according to id to article. I hope the gods can advise
whether the mysql data inventory string is the same as storing numbers that occupy memory?