$addFields for computed fields in MongoDB - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to add a new field 'totalPrice' by multiplying 'price' and 'quantity'.

MongoDB

db.orders.aggregate([{ $addFields: { totalPrice: { $multiply: ["$price", [1]] } } }])

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

A"amount"

B"quantity"

C"$total"

D"$quantity"

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting the '$' prefix before field names.

Using the wrong field name without '$'.

In MongoDB aggregation, to refer to a field, prefix it with '$'. So to multiply 'price' and 'quantity', use "$quantity".

2fill in blank

medium

Complete the code to add a field 'fullName' by concatenating 'firstName' and 'lastName' with a space.

MongoDB

db.users.aggregate([{ $addFields: { fullName: { $concat: ["$firstName", [1], "$lastName"] } } }])

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

A" "

B"-"

C","

D"_"

Attempts:

3 left

💡 Hint

Common Mistakes

Using a dash or underscore instead of a space.

Forgetting to put the separator inside quotes.

To join first and last names with a space, use a space string " " inside $concat.

3fill in blank

hard

Fix the error in the code to add a field 'discountedPrice' by subtracting 'discount' from 'price'.

MongoDB

db.sales.aggregate([{ $addFields: { discountedPrice: { $subtract: ["price", [1]] } } }])

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

A"$discount"

B"discount"

C"$price"

D"amount"

Attempts:

3 left

💡 Hint

Common Mistakes

Omitting the '$' prefix before field names.

Using the wrong field name.

Field names in aggregation expressions must be prefixed with '$'. So use "$discount" to refer to the discount field.

4fill in blank

hard

Fill both blanks to add a field 'averageScore' by dividing 'totalScore' by 'numTests'.

MongoDB

db.students.aggregate([{ $addFields: { averageScore: { $divide: ["[1]", "[2]"] } } }])

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

A$totalScore

B$numTests

CtotalScore

DnumTests

Attempts:

3 left

💡 Hint

Common Mistakes

Using field names without '$' prefix.

Swapping numerator and denominator.

Use "$totalScore" and "$numTests" to refer to the fields inside the $divide operator.

5fill in blank

hard

Fill all three blanks to add a field 'summary' that concatenates uppercase 'category', a colon, and 'description'.

MongoDB

db.products.aggregate([{ $addFields: { summary: { $concat: [[1], [2], [3]] } } }])

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

A{'$toUpper': '$category'}

B": "

C$description

D$category

Attempts:

3 left

💡 Hint

Common Mistakes

Not using $toUpper for uppercase conversion.

Forgetting quotes around the colon and space string.

Using wrong field names.

Use $toUpper to convert 'category' to uppercase, then add a colon and space string ": ", then add 'description'.