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one to many vs many to many - Books and authors


The bidirectional associations allow you to navigate both sides of this relationship both in Object space as well as in JPA/Hibernate Query Language.

In your example, a database many-to-many association is mandatory (meaning you have a BOOK, an AUTHOR and a BOOK_AUTHOR link table). Hibernate offers two possibilities for mapping this relationship:

  1. You can model this with two entities: Book and Author, each one having a @ManyToMany association to the other (one being the owning side while the other being the inverse one)

  2. You can have three entities: Book, Author and BookAuthor and this time Book have a @OneToMany association to BookAuthor and Author has also a @OneToMany association to BookAuthor. This option allows you two map additional link table columns (BOOK_AUTHOR creation_time).


Categories : Database

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Compute the total number of accepted papers that are authored by at least two authors
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