$addToSet for unique array additions in MongoDB - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to add a unique value to the 'tags' array using $addToSet.

MongoDB

db.collection.updateOne({ _id: 1 }, { $[1]: { tags: "mongodb" } })

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

AaddToSet

Bpush

Cset

DaddUnique

Attempts:

3 left

💡 Hint

Common Mistakes

Using $push instead of $addToSet, which can add duplicates.

Using $set which replaces the whole array.

The $addToSet operator adds a value to an array only if it does not already exist, ensuring uniqueness.

2fill in blank

medium

Complete the code to add multiple unique values to the 'tags' array using $addToSet with $each.

MongoDB

db.collection.updateOne({ _id: 2 }, { $addToSet: { tags: { $[1]: ["nodejs", "database"] } } })

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

Aall

Bmultiple

Cmany

Deach

Attempts:

3 left

💡 Hint

Common Mistakes

Using $push with $each but forgetting $addToSet for uniqueness.

Using incorrect modifier names like $all or $many.

The $each modifier allows adding multiple values uniquely with $addToSet.

3fill in blank

hard

Fix the error in the update command to correctly add a unique value to the 'categories' array.

MongoDB

db.collection.updateOne({ _id: 3 }, { $[1]: { categories: "tech" } })

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

Apush

BaddToSet

Cset

Dappend

Attempts:

3 left

💡 Hint

Common Mistakes

Using $push which can add duplicates.

Using $set which replaces the whole array.

To add a unique value to an array, use $addToSet. Using $push adds duplicates.

4fill in blank

hard

Fill both blanks to add multiple unique tags to the 'labels' array.

MongoDB

db.collection.updateOne({ _id: 4 }, { $[1]: { labels: { $[2]: ["urgent", "review"] } } })

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

AaddToSet

Bpush

Ceach

Dset

Attempts:

3 left

💡 Hint

Common Mistakes

Using $push instead of $addToSet.

Forgetting to use $each when adding multiple values.

Use $addToSet with $each to add multiple unique values to an array.

5fill in blank

hard

Fill all three blanks to add a unique uppercase tag to the 'tags' array using an aggregation pipeline update.

MongoDB

db.collection.updateOne({ _id: 5 }, [ { $[1]: { [2]: { $toUpper: "[3]" } } } ])

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

AconcatArrays

Burgent

CaddToSet

Dtags

Attempts:

3 left

💡 Hint

Common Mistakes

Using $concatArrays which rebuilds the array but allows duplicates.

Using $set which replaces the array.

Wrong field name or forgetting to uppercase.

In an aggregation pipeline update stage, use $addToSet (BLANK_1) on the tags field (BLANK_2) with the uppercase expression on urgent (BLANK_3) to add a unique uppercase tag.