Unique index behavior in MongoDB - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a unique index on the "email" field in MongoDB.

MongoDB

db.users.createIndex({ email: 1 }, { unique: [1] })

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

Atrue

Bfalse

Cunique

D1

Attempts:

3 left

💡 Hint

Common Mistakes

Using a string instead of a boolean for the unique option.

Setting unique to false which does not enforce uniqueness.

Setting unique: true ensures the index enforces uniqueness on the field.

2fill in blank

medium

Complete the code to insert a document that violates a unique index on "username".

MongoDB

db.users.insertOne({ username: [1], age: 25 })

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

A"unique"

Bjohn_doe

C25

D"john_doe"

Attempts:

3 left

💡 Hint

Common Mistakes

Not quoting string values causing syntax errors.

Using a number instead of a string for username.

String values must be quoted in MongoDB insert commands.

3fill in blank

hard

Fix the error in the unique index creation by completing the code.

MongoDB

db.users.createIndex({ email: 1 }, { [1]: true })

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

AuniqueIndex

Bunique

Cunique_key

Dunique_value

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect option names like uniqueIndex or unique_key.

Misspelling the option name.

The correct option name to enforce uniqueness is unique.

4fill in blank

hard

Fill both blanks to create a unique index on "phone" field in descending order.

MongoDB

db.contacts.createIndex({ phone: [1] }, { [2]: true })

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

A-1

B1

Cunique

Dindex

Attempts:

3 left

💡 Hint

Common Mistakes

Using 1 instead of -1 for descending order.

Using index instead of unique for uniqueness.

Use -1 for descending order and unique: true to enforce uniqueness.

5fill in blank

hard

Fill all three blanks to create a unique compound index on "firstName" ascending and "lastName" descending.

MongoDB

db.users.createIndex({ firstName: [1], lastName: [2] }, { [3]: true })

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

A1

B-1

Cunique

Dindex

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up ascending and descending values.

Using index instead of unique for uniqueness.

Use 1 for ascending, -1 for descending, and unique: true to enforce uniqueness on the compound index.