Embedded documents (nested objects) in MongoDB - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is an embedded document in MongoDB?

An embedded document is a document stored inside another document as a nested object. It helps group related data together in one place.

beginner

How do you represent a nested object in a MongoDB document?

You use curly braces inside a field to create a nested object. For example: { "address": { "city": "Paris", "zip": "75000" } }

intermediate

Why use embedded documents instead of separate collections?

Embedded documents keep related data together, making it faster to read and easier to manage small related data without extra queries.

intermediate

How do you query a field inside an embedded document in MongoDB?

Use dot notation to access nested fields. For example: db.collection.find({ "address.city": "Paris" }) finds documents where city inside address is Paris.

beginner

Can embedded documents contain arrays in MongoDB?

Yes, embedded documents can have arrays as values, and those arrays can contain objects or simple values.

What does an embedded document in MongoDB allow you to do?

A Encrypt data automatically

B Create a new database

C Run SQL queries

D Store related data inside a single document

Embedded documents store related data inside one document, grouping information together.

How do you access a nested field 'city' inside 'address' in a MongoDB query?

A address->city

B address_city

C address.city

D city.address

MongoDB uses dot notation like 'address.city' to access nested fields.

Which of these is a correct example of an embedded document?

A { name: 'John', address: { city: 'NY', zip: '10001' } }

B { name: 'John', city: 'NY', zip: '10001' }

C [ { city: 'NY' }, { zip: '10001' } ]

D name: 'John', address: 'NY'

Option A shows a nested object inside the 'address' field, which is an embedded document.

Why might you choose embedded documents over references in MongoDB?

A To increase database size

B To reduce the number of queries needed to get related data

C To separate unrelated data

D To use SQL joins

Embedding related data reduces queries by storing it together.

Can embedded documents contain arrays in MongoDB?

A Yes, arrays can be inside embedded documents

B No, arrays are not allowed

C Only arrays of numbers are allowed

D Only arrays of strings are allowed

Embedded documents can contain arrays of any type, including objects.

Explain what embedded documents are in MongoDB and why they are useful.

Think about how you might store an address inside a user profile.

Describe how to query a nested field inside an embedded document in MongoDB.

Remember the format: 'field.subfield' in the query.