Use embedded documents for one-to-many relationships. Embedding connected data in a single document reduces the number of read operations required to retrieve data. Structure your schema so your application receives all required information in a single read operation. For example, use the embedded one-to-many model for the following relationships:
Country to major cities
Author to books
Student to classes
Example
The example schema contains three entities, with address one and address two belonging to the same patron:
// patron document{ _id: "joe", name: "Joe Bookreader"}
// address one{ street: "123 Fake Street", city: "Faketon", state: "MA", zip: "12345"}
// address two{ street: "1 Some Other Street", city: "Boston", state: "MA", zip: "12345"}Embedded Document Pattern
In this example the application needs to display information for the patron and both address objects on a single page. To retrieve all necessary information with a single query, embed the address one and address two information inside the patron document:
{ _id: "joe", name: "Joe Bookreader", addresses: [ { street: "123 Fake Street", city: "Faketon", state: "MA", zip: "12345" }, { street: "1 Some Other Street", city: "Boston", state: "MA", zip: "12345" } ] }