Why the aggregation pipeline is needed in MongoDB - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to start an aggregation pipeline on the 'orders' collection.

MongoDB

db.orders.[1]([{ $match: { status: 'shipped' } }])

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

Ainsert

Bfind

Cupdate

Daggregate

Attempts:

3 left

💡 Hint

Common Mistakes

Using find() instead of aggregate() for complex data processing.

Trying to use insert() or update() which modify data, not process it.

The aggregate method starts an aggregation pipeline in MongoDB.

2fill in blank

medium

Complete the code to filter documents where 'age' is greater than 25 in the aggregation pipeline.

MongoDB

db.users.aggregate([{ $match: { age: { [1]: 25 } } }])

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

A$lt

B$eq

C$gt

D$ne

Attempts:

3 left

💡 Hint

Common Mistakes

Using $lt which means less than, opposite of what is needed.

Using $eq which means equal, not greater than.

The $gt operator means 'greater than' in MongoDB queries.

3fill in blank

hard

Fix the error in the aggregation stage that groups documents by 'category' and counts them.

MongoDB

db.products.aggregate([{ $group: { _id: '$category', count: { [1]: 1 } } }])

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

A$sum

B$avg

C$max

D$min

Attempts:

3 left

💡 Hint

Common Mistakes

Using $avg which calculates average, not count.

Using $max or $min which find max or min values, not counts.

The $sum operator counts the number of documents in each group.

4fill in blank

hard

Fill both blanks to project only the 'name' and 'price' fields in the aggregation pipeline.

MongoDB

db.items.aggregate([{ $project: { [1]: 1, [2]: 1, _id: 0 } }])

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

Aname

Bprice

Ccategory

Dquantity

Attempts:

3 left

💡 Hint

Common Mistakes

Including fields not needed like 'category' or 'quantity'.

Forgetting to exclude _id if not wanted.

Projecting 'name' and 'price' fields includes only these fields in the output.

5fill in blank

hard

Fill all three blanks to filter documents with 'score' greater than 80, then sort by 'score' descending, and limit to 5 results.

MongoDB

db.scores.aggregate([ { $match: { score: { [1]: 80 } } }, { $sort: { score: [2] } }, { $limit: [3] } ])

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

A$gt

B-1

C5

D1

Attempts:

3 left

💡 Hint

Common Mistakes

Using $lt instead of $gt for filtering.

Sorting ascending (1) instead of descending (-1).

Setting limit to a wrong number.

Use $gt to filter scores greater than 80, -1 to sort descending, and 5 to limit results to 5.