Many-to-many mapping

In many-to-many relationship one more entities are mapped to one or more entities.

Example

books-authors

students-teachers

customer-products

One book can have one or more authors.

One author can write one or more books.

Books-authors modelling

We can create two collections, one for books and other for authors.

author collection

{ "_id" : 1, "name" : "Herbert", "books_ids" : [ 1 ] }

{ "_id" : 2, "name" : "Kanetkar", "books_ids" : [ 1, 2 ] }

books collection

{ "_id" : 1, "title" : "learn java", "author_ids" : [ 1, 2 ] }

{ "_id" : 2, "title" : "Explore java", "author_ids" : [ 2 ] }

Document in books collection contains author_ids array, which refers to a document in author collection.

Document in author collection contain books_ids, which refers to a document in books collection.

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