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- Model Embedded One-to-One Relationships Between Documents
Model Embedded One-to-One Relationships Between Documents¶
Overview¶
Data in MongoDB has a flexible schema. Collections do not enforce document structure. Decisions that affect how you model data can affect application performance and database capacity. See Data Modeling Considerations for MongoDB Applications for a full high level overview of data modeling in MongoDB.
This document describes a data model that uses embedded documents to describe relationships between connected data.
Pattern¶
Consider the following example that maps patron and address
relationships. The example illustrates the advantage of embedding over
referencing if you need to view one data entity in context of the
other. In this one-to-one relationship between patron
and
address
data, the address
belongs to the patron
.
In the normalized data model, the address
contains a reference to
the parent
.
If the address
data is frequently retrieved with the name
information, then with referencing, your application needs to issue
multiple queries to resolve the reference. The better data model would
be to embed the address
data in the patron
data, as in the
following document:
With the embedded data model, your application can retrieve the complete patron information with one query.