Dot notation for embedded documents in MongoDB - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to find all documents where the city is 'Paris'.

MongoDB

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

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

Astreet

Bcity

Czipcode

Dcountry

Attempts:

3 left

💡 Hint

Common Mistakes

Using the top-level field name instead of the embedded field.

Using incorrect field names like 'street' or 'zipcode' when searching for city.

The dot notation accesses the embedded field 'city' inside 'address'. So "address.city" is correct.

2fill in blank

medium

Complete the code to update the zipcode to '75001' for users living in 'Paris'.

MongoDB

db.users.updateMany({"address.city": "Paris"}, {$set: {"address.[1]": "75001"}})

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

Astreet

Bcountry

Ccity

Dzipcode

Attempts:

3 left

💡 Hint

Common Mistakes

Trying to update the 'city' field instead of 'zipcode'.

Using top-level fields instead of dot notation.

We use "address.zipcode" to update the zipcode inside the embedded address document.

3fill in blank

hard

Fix the error in the query to find users with phone number '123-4567' inside the 'contact' embedded document.

MongoDB

db.users.find({"contact.[1]": "123-4567"})

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

Aphone

Bemail

Caddress

Dname

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'email' or 'address' instead of 'phone'.

Not using dot notation for embedded fields.

The phone number is stored in the 'phone' field inside the 'contact' embedded document, so use "contact.phone".

4fill in blank

hard

Fill both blanks to find users whose address city is 'London' and update their contact email to '[e-mail]'.

MongoDB

db.users.updateMany({"address.[1]": "London"}, {$set: {"contact.[2]": "[e-mail]"}})

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

Acity

Bphone

Cemail

Dzipcode

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up 'phone' and 'email' fields.

Using wrong embedded document names.

We query by "address.city" and update "contact.email".

5fill in blank

hard

Fill all three blanks to create a document with embedded 'profile' containing 'username' and 'age', and insert it into the 'users' collection.

MongoDB

db.users.insertOne({"profile": {"[1]": "alice123", "[2]": [3])

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

Ausername

Bage

C30

Demail

Attempts:

3 left

💡 Hint

Common Mistakes

Putting the age value in quotes (should be a number).

Using wrong field names like 'email' instead of 'username' or 'age'.

The embedded document 'profile' has fields 'username' and 'age'. The age value is a number, so use 30 without quotes.

Practice

1. What does dot notation in MongoDB allow you to do with embedded documents?

easy

A. Access nested fields inside embedded documents

B. Create new collections automatically

C. Encrypt data within documents

D. Delete entire databases

Solution

1. Step 1: Understand dot notation purpose

   Dot notation is used to reach inside nested or embedded documents to access specific fields.

2. Step 2: Compare with other options

   Creating collections, encrypting data, or deleting databases are unrelated to dot notation.

3. Final Answer:

   Access nested fields inside embedded documents -> Option A

4. Quick Check:

   Dot notation = Access nested fields [OK]

Hint: Dot notation accesses nested fields using dots [OK]

Common Mistakes:

• Thinking dot notation creates collections
• Confusing dot notation with encryption
• Assuming dot notation deletes data

2. Which of the following is the correct syntax to query the field address.city in MongoDB?

easy

A. { address.city: 'New York' }

B. { address->city: 'New York' }

C. { 'address.city': 'New York' }

D. { address[city]: 'New York' }

Solution

1. Step 1: Understand dot notation syntax in queries

   Field names with dots must be quoted as a single string in MongoDB queries.

2. Step 2: Evaluate each option

   { 'address.city': 'New York' } uses quotes correctly around 'address.city'. Options A, C, and D use invalid syntax.

3. Final Answer:

   { 'address.city': 'New York' } -> Option C

4. Quick Check:

   Quotes needed for dot field names = { 'address.city': 'New York' } [OK]

Hint: Quote dot notation keys in queries [OK]

Common Mistakes:

• Not quoting dot notation keys
• Using arrows or brackets instead of dots
• Using unquoted keys with dots

3. Given the collection documents:

{ name: 'Alice', contact: { phone: '1234', email: '[e-mail]' } }

What will the query db.collection.find({ 'contact.phone': '1234' }) return?

medium

A. Documents where contact.phone equals '1234'

B. Documents where contact.email equals '1234'

C. Documents where name equals '1234'

D. No documents, syntax error

Solution

1. Step 1: Understand the query filter

   The query filters documents where the embedded field contact.phone equals '1234'.

2. Step 2: Match with document data

   The example document has contact.phone as '1234', so it matches and will be returned.

3. Final Answer:

   Documents where contact.phone equals '1234' -> Option A

4. Quick Check:

   Dot notation filters embedded fields = Documents where contact.phone equals '1234' [OK]

Hint: Dot notation filters nested fields directly [OK]

Common Mistakes:

• Confusing phone with email field
• Thinking dot notation causes syntax error
• Assuming it filters top-level fields only

4. What is wrong with this MongoDB query to update the city in an embedded address document?

db.users.updateOne({ name: 'Bob' }, { $set: { address.city: 'Boston' } })

medium

A. Update operator $set is incorrect

B. Field name with dot must be quoted as a string

C. Collection name should be 'user' not 'users'

D. Query filter is missing

Solution

1. Step 1: Check update syntax for embedded fields

   When using dot notation in update keys, the field name must be quoted as a string.

2. Step 2: Analyze the given query

   The query uses address.city without quotes, which causes a syntax error.

3. Final Answer:

   Field name with dot must be quoted as a string -> Option B

4. Quick Check:

   Quote dot notation keys in updates = Field name with dot must be quoted as a string [OK]

Hint: Quote dot notation keys in update documents [OK]

Common Mistakes:

• Not quoting dot notation keys in $set
• Misusing update operators
• Assuming collection name is wrong

5. You have documents with nested structure:

{ _id: 1, profile: { name: 'Eve', contacts: { email: '[e-mail]', phone: '555' } } }

How do you write a query to find documents where the phone number is '555' using dot notation?

hard

A. { 'profile.contacts': { phone: '555' } }

B. { profile.contacts.phone: '555' }

C. { profile.contacts['phone']: '555' }

D. { 'profile.contacts.phone': '555' }

Solution

1. Step 1: Identify the full path to the nested field

   The phone field is inside contacts, which is inside profile, so the path is profile.contacts.phone.

2. Step 2: Use dot notation with quotes in query

   To query nested fields, use quotes around the full dot notation key: 'profile.contacts.phone'.

3. Final Answer:

   { 'profile.contacts.phone': '555' } -> Option D

4. Quick Check:

   Quote full dot notation path in query = { 'profile.contacts.phone': '555' } [OK]

Hint: Quote full dot notation path in queries [OK]

Common Mistakes:

• Not quoting dot notation keys
• Using object instead of dot notation in query
• Using brackets inside dot notation keys