Embedded documents (nested objects) in MongoDB - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to insert a document with an embedded address object.

MongoDB

db.users.insertOne({ name: "Alice", address: [1] })

Drag options to blanks, or click blank then click option'

A"123 Main St, Springfield"

B["123 Main St", "Springfield"]

C{ street: "123 Main St", city: "Springfield" }

Dnull

Attempts:

3 left

💡 Hint

Common Mistakes

Using an array instead of an object for the embedded document.

Using a string instead of an object for the embedded document.

The embedded document must be an object with key-value pairs, not an array or string.

2fill in blank

medium

Complete the query to find users living in the city 'Springfield'.

MongoDB

db.users.find({ "address.[1]": "Springfield" })

Drag options to blanks, or click blank then click option'

Astreet

Bcity

Czip

Dstate

Attempts:

3 left

💡 Hint

Common Mistakes

Using the wrong nested key like 'street' or 'zip'.

Not using quotes around the dot notation field.

To query a nested field, use dot notation with the key name. Here, 'city' is the nested key.

3fill in blank

hard

Fix the error in the update query to set the user's street to '456 Elm St'.

MongoDB

db.users.updateOne({ name: "Alice" }, { $set: { "address.[1]": "456 Elm St" } })

Drag options to blanks, or click blank then click option'

Astreet

Baddress

Czip

Dcity

Attempts:

3 left

💡 Hint

Common Mistakes

Trying to update the whole address object instead of just the street.

Using the wrong nested key like 'city' or 'zip'.

The street field inside the embedded address document must be updated using 'address.street'.

4fill in blank

hard

Fill both blanks to create a document with a nested contact object containing email and phone.

MongoDB

db.contacts.insertOne({ name: "Bob", contact: { [1]: "[e-mail]", [2]: "123-456-7890" } })

Drag options to blanks, or click blank then click option'

Aemail

Bphone

Caddress

Dname

Attempts:

3 left

💡 Hint

Common Mistakes

Using keys like 'address' or 'name' inside the contact object.

Mixing up the keys for email and phone.

The nested contact object should have keys 'email' and 'phone' with their respective values.

5fill in blank

hard

Fill all three blanks to query documents where the nested 'contact.email' ends with '@example.com'.

MongoDB

db.contacts.find({ "contact.[1]": { [2]: [3] } })

Drag options to blanks, or click blank then click option'

Aphone

B$regex

C"@example.com$"

Demail

Attempts:

3 left

💡 Hint

Common Mistakes

Using the wrong nested key like 'phone'.

Using an incorrect operator instead of $regex.

Not using quotes around the regex pattern.

To filter by a pattern in a nested field, use dot notation for the field, the $regex operator, and the regex pattern string.

Practice

1. What is an embedded document in MongoDB?

easy

A. A document stored inside another document as a nested object

B. A separate collection linked by an ID

C. A document stored in a different database

D. A document stored as a file on disk

Solution

1. Step 1: Understand MongoDB document structure

   MongoDB stores data in documents, which can contain nested objects called embedded documents.

2. Step 2: Identify embedded document meaning

   An embedded document is a document inside another document, not a separate collection or file.

3. Final Answer:

   A document stored inside another document as a nested object -> Option A

4. Quick Check:

   Embedded document = nested object inside document [OK]

Hint: Think of a box inside another box holding related info [OK]

Common Mistakes:

• Confusing embedded documents with references
• Thinking embedded documents are separate collections
• Assuming embedded documents are stored outside the database

2. Which of the following is the correct way to insert an embedded document in MongoDB?

easy

A. db.collection.insertOne([{name: 'Alice'}, {address: {city: 'NY', zip: 10001}}])

B. db.collection.insertOne({name: 'Alice'}, {address: {city: 'NY', zip: 10001}})

C. db.collection.insertOne(name: 'Alice', address: {city: 'NY', zip: 10001})

D. db.collection.insertOne({name: 'Alice', address: {city: 'NY', zip: 10001}})

Solution

1. Step 1: Review MongoDB insertOne syntax

   insertOne takes a single document object with fields and values, including nested objects.

2. Step 2: Check each option's syntax

   db.collection.insertOne({name: 'Alice', address: {city: 'NY', zip: 10001}}) correctly nests the address object inside the main document. Others have syntax errors or wrong structure.

3. Final Answer:

   db.collection.insertOne({name: 'Alice', address: {city: 'NY', zip: 10001}}) -> Option D

4. Quick Check:

   Nested object inside one document = correct insert [OK]

Hint: Use one object with nested braces for embedded docs [OK]

Common Mistakes:

• Passing multiple objects instead of one
• Missing curly braces around nested document
• Using array instead of object for embedded document

3. Given the document { name: 'Bob', contact: { email: '[e-mail]', phone: '1234' } }, what will the query db.users.find({ 'contact.email': '[e-mail]' }) return?

medium

A. No documents, because nested fields can't be queried

B. All documents where contact.email equals '[e-mail]'

C. Documents where name equals '[e-mail]'

D. Documents where contact is exactly '[e-mail]'

Solution

1. Step 1: Understand dot notation in queries

   MongoDB uses dot notation to query fields inside embedded documents.

2. Step 2: Analyze the query

   The query looks for documents where the embedded field contact.email matches the given value.

3. Final Answer:

   All documents where contact.email equals '[e-mail]' -> Option B

4. Quick Check:

   Dot notation queries embedded fields correctly [OK]

Hint: Use dot notation to access nested fields in queries [OK]

Common Mistakes:

• Trying to match entire embedded document instead of field
• Using wrong field name without dot notation
• Assuming nested fields can't be queried

4. What is wrong with this update query to change the city in an embedded address document?
db.users.updateOne({name: 'Eve'}, {address.city: 'LA'})

medium

A. The field name should not use dot notation

B. The query filter is incorrect

C. The update document is missing the $set operator

D. updateOne cannot update embedded documents

Solution

1. Step 1: Recall updateOne syntax

   updateOne requires an update operator like $set to specify fields to change.

2. Step 2: Identify missing $set operator

   The query tries to update address.city directly without $set, which is invalid syntax.

3. Final Answer:

   The update document is missing the $set operator -> Option C

4. Quick Check:

   Updates need $set for field changes [OK]

Hint: Always use $set to update fields, including nested ones [OK]

Common Mistakes:

• Forgetting $set in update document
• Using dot notation incorrectly in filter
• Thinking updateOne can't change nested fields

5. You want to store multiple phone numbers inside a user's document using embedded documents. Which schema design is best?

hard

A. { name: 'Sam', phones: [{ type: 'home', number: '111' }, { type: 'work', number: '222' }] }

B. { name: 'Sam', phone1: '111', phone2: '222' }

C. { name: 'Sam', phones: { home: '111', work: '222' } }

D. { name: 'Sam', phones: '111,222' }

Solution

1. Step 1: Understand storing multiple embedded documents

   To store multiple related items, use an array of embedded documents for flexibility and clarity.

2. Step 2: Compare options

   { name: 'Sam', phones: [{ type: 'home', number: '111' }, { type: 'work', number: '222' }] } uses an array of objects with type and number, which is clear and scalable. Others are less flexible or harder to query.

3. Final Answer:

   { name: 'Sam', phones: [{ type: 'home', number: '111' }, { type: 'work', number: '222' }] } -> Option A

4. Quick Check:

   Array of embedded docs best for multiple related items [OK]

Hint: Use arrays of objects for multiple related embedded documents [OK]

Common Mistakes:

• Storing multiple values as comma-separated string
• Using separate fields for each phone number
• Using a single object without array for multiple items