One to One Relationships: Overview

• What is a "one to one" relationship?

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  • One item maps directly to another item
  • Example: Person --> Birthdate
  • Example: Vehicle --> Registration Number

• When would you use a "one to one" relationship?

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  • When the amount of data is too large for a single item
  • Split the data into separate collections
  • Provide a common key

• What is a normalized data model?

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  • Collections of data which share common identifying keys
  • Customers --> Purchases --> Products

• How can you build "one to one" relationships in MongoDB?

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  • Use either the "manual", the "embedded", or the "DBRef" approach