$sum accumulator in MongoDB - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to sum the values of the "score" field in the aggregation.

MongoDB

db.scores.aggregate([{ $group: { _id: null, totalScore: { $sum: "$"[1] } } }])

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

Atotal

Bscore

Cvalue

Damount

Attempts:

3 left

💡 Hint

Common Mistakes

Using a field name that does not exist in the documents.

Forgetting to include the $ sign before the field name.

The $sum accumulator sums the values of the specified field. Here, we sum the "score" field.

2fill in blank

medium

Complete the code to sum the values of the "quantity" field grouped by "category".

MongoDB

db.products.aggregate([{ $group: { _id: "$"[1], totalQuantity: { $sum: "$quantity" } } }])

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

Acategory

Bprice

Cname

Dtype

Attempts:

3 left

💡 Hint

Common Mistakes

Grouping by a field that does not exist.

Using the wrong field name for grouping.

The _id field in $group specifies the grouping key. Here, we group by "category" to sum quantities per category.

3fill in blank

hard

Fix the error in the aggregation pipeline to correctly sum the "amount" field.

MongoDB

db.transactions.aggregate([{ $group: { _id: null, totalAmount: { $sum: [1] } } }])

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

A$amount

B"amount"

Camount

D$"amount"

Attempts:

3 left

💡 Hint

Common Mistakes

Putting the field name in quotes inside $sum.

Forgetting the $ sign before the field name.

The $sum accumulator requires the field to be prefixed with a $ sign without quotes, like $amount.

4fill in blank

hard

Fill both blanks to sum the "price" field grouped by "brand".

MongoDB

db.items.aggregate([{ $group: { _id: "$"[1], totalPrice: { $sum: "$"[2] } } }])

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

Abrand

Bcategory

Cprice

Dcost

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up the grouping field and the sum field.

Using incorrect field names.

Group by the "brand" field and sum the "price" field values.

5fill in blank

hard

Fill all three blanks to sum the "score" field grouped by uppercase "player" names.

MongoDB

db.games.aggregate([{ $group: { _id: { [1]: { $toUpper: "$"[2] } }, totalScore: { $sum: "$"[3] } } }])

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

A$toUpper

Bplayer

Cscore

D$toLower

Attempts:

3 left

💡 Hint

Common Mistakes

Not using an expression for _id when transforming values.

Using wrong field names for sum or group.

Use { $toUpper: "$player" } to group by uppercase player names and sum their scores.