One-to-many referencing pattern in MongoDB - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to find all orders for a customer with ID 123.

MongoDB

db.orders.find({ customer_id: [1] })

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

A123

B"123"

C"customer_id"

DObjectId("123")

Attempts:

3 left

💡 Hint

Common Mistakes

Using quotes around the number when the ID is stored as a number.

Using ObjectId when the ID is a simple number.

The customer_id field stores the customer's ID as a number, so we query with 123 without quotes.

2fill in blank

medium

Complete the code to insert a new order referencing customer ID 456.

MongoDB

db.orders.insertOne({ order_id: 1, customer_id: [1], items: 0 })

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

A456

B"customer_456"

CObjectId("456")

D"456"

Attempts:

3 left

💡 Hint

Common Mistakes

Using a string instead of a number for customer_id.

Using ObjectId when not appropriate.

The customer_id should match the type used in the database, which is a number here.

3fill in blank

hard

Fix the error in the query to find orders for customer ID 789.

MongoDB

db.orders.find({ customer_id: [1] })

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

A"789"

B789

CObjectId("789")

Dcustomer_id

Attempts:

3 left

💡 Hint

Common Mistakes

Using a string or ObjectId instead of a number.

Using the field name as a value.

The customer_id is stored as a number, so the query must use the number 789 without quotes or ObjectId.

4fill in blank

hard

Fill both blanks to create a query that finds orders with more than 2 items for customer ID 101.

MongoDB

db.orders.find({ customer_id: [1], items: { $[2]: 2 } })

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

A101

Bgt

Cgte

Dlt

Attempts:

3 left

💡 Hint

Common Mistakes

Using $gte instead of $gt for strictly more than 2.

Using the wrong customer ID.

We query for customer_id 101 and use $gt to find orders with more than 2 items.

5fill in blank

hard

Fill all three blanks to update the customer name for customer ID 202.

MongoDB

db.customers.updateOne({ _id: [1] }, { $[2]: { name: [3] } })

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

A202

Bset

C"Alice"

D"202"

Attempts:

3 left

💡 Hint

Common Mistakes

Using string "202" instead of number 202 for _id.

Using wrong update operator like $update.

Not quoting the new name string.

The query matches the customer with _id 202 (number), uses $set to update, and sets the name to "Alice".