Schema Design. Data Models¶ Data in MongoDB has a flexible schema.
Collections do not enforce document structure. This flexibility gives you data-modeling choices to match your application and its performance requirements. Database References. MongoDB does not support joins.
In MongoDB some data is denormalized, or stored with related data in documents to remove the need for joins. However, in some cases it makes sense to store related information in separate documents, typically in different collections or databases. MongoDB applications use one of two methods for relating documents: Nosql - MongoDB embedded documents vs. referencing by unique ObjectIds for a system user profile.