Introduction to Modeling One-to-One Relationships

One-to-one relationships in MongoDB occur when a document in one collection is related to a single document in another collection. While MongoDB is known for its flexible schema, modeling one-to-one relationships can be done in several ways. In this guide, we'll explore how to model one-to-one relationships in MongoDB with sample code.

Option 1: Embedding Documents

One way to model one-to-one relationships is by embedding one document within another. This is useful when both documents share similar characteristics. For example:

{
    _id: 1,
    name: "User",
    profile: {
        fullName: "John Doe",
        email: "johndoe@example.com"
    }
}
        

Option 2: Referencing Documents

Another approach is to reference one document from another using an identifier, typically the ObjectId. This approach is beneficial when the two documents have distinct structures. For example:

// Users collection
{
    _id: 1,
    name: "User",
    profile: 2 // Reference to the profile document
}
// Profiles collection
{
    _id: 2,
    fullName: "John Doe",
    email: "johndoe@example.com"
}
        

Pros and Cons

Each approach has its pros and cons. Embedding is efficient for read operations and ensures data consistency, but it can lead to data duplication. Referencing is more storage-efficient but requires additional queries for retrieval. The choice depends on your specific use case and performance requirements.

Conclusion

Modeling one-to-one relationships in MongoDB requires careful consideration of your data structure and usage patterns. Whether you choose to embed or reference documents, it's important to design your schema to best suit your application's needs and performance requirements.