Database (two) - many-related operations

On one we built four tables person_publisher, person_author, person_book, person_author_book:

 

 

 Finally, a table is many-created automatically by the system.

The default primary key in the Book publisher associated Publisher, generates a publisher_id field.

(1) to obtain the object named gong (note that we get is an object)

author_obj = models.Author.objects.get(name="gong")
print(author_obj)
输出：author_name:gong

(2) create- named as the author of a new book gong

author_obj.book.create (title = " ZABBIX Mastering " , publisher_id =. 3)

(3) add- author is gong to add a book (java)

book_obj = models.Book.objects.get(title="java")
author_obj.book.add(book_obj)

(4) remove- is gong to delete a book author (python)

book_obj = models.Book.objects.get(title="java")
author_obj.book.remove(book_obj)

(5) as a white author, delete a book, id book is 4

author_obj.book.remove(4)

(6) clear- the author of the book associated gong, delete all empty

author_obj.book.clear()