updateMany method in MongoDB - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to update all documents where age is greater than 25.

MongoDB

db.collection.updateMany({ age: { $[1]: 25 } }, { $set: { status: "active" } })

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

Aeq

Bgt

Clt

Dne

Attempts:

3 left

💡 Hint

Common Mistakes

Using $lt which means less than.

Using $eq which means equal to.

The $gt operator means 'greater than', so it selects documents where age is more than 25.

2fill in blank

medium

Complete the code to set the field "verified" to true for all users with status "pending".

MongoDB

db.users.updateMany({ status: "[1]" }, { $set: { verified: true } })

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

Aactive

Bdeleted

Cinactive

Dpending

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'active' which means already approved.

Using 'inactive' which means disabled.

We want to update users whose status is exactly "pending".

3fill in blank

hard

Fix the error in the updateMany query to increment the "score" field by 10 for all documents.

MongoDB

db.scores.updateMany({}, { $[1]: { score: 10 } })

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

Ainc

Bpush

Cadd

Dset

Attempts:

3 left

💡 Hint

Common Mistakes

Using $set which replaces the field value.

Using $push which is for arrays.

The $inc operator increments a numeric field by the specified value.

4fill in blank

hard

Fill both blanks to update the "status" to "archived" for documents where "lastLogin" is less than 2020.

MongoDB

db.accounts.updateMany({ lastLogin: { $[1]: 2020 } }, { $[2]: { status: "archived" } })

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

Alt

Bgt

Cset

Dinc

Attempts:

3 left

💡 Hint

Common Mistakes

Using $gt instead of $lt for the date comparison.

Using $inc instead of $set for updating a string field.

$lt means less than, so it selects documents with lastLogin before 2020. $set updates the status field.

5fill in blank

hard

Fill all three blanks to increment the "visits" by 1 for users with "role" equal to "member".

MongoDB

db.users.updateMany({ role: "[1]" }, { $[2]: { visits: [3] } })

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

Amember

Binc

C1

Dset

Attempts:

3 left

💡 Hint

Common Mistakes

Using $set instead of $inc for incrementing.

Using a wrong role name.

We select users with role "member". Then we use $inc to add 1 to the visits field.

Practice

1. What does the updateMany method do in MongoDB?

easy

A. Inserts multiple new documents

B. Deletes multiple documents at once

C. Finds a single document by ID

D. Updates multiple documents that match a filter

Solution

1. Step 1: Understand the purpose of updateMany

   The updateMany method is designed to update all documents that match a given filter in a collection.

2. Step 2: Compare with other operations

   Deleting documents is done by deleteMany, inserting by insertMany, and finding by findOne. So, only updateMany updates multiple documents.

3. Final Answer:

   Updates multiple documents that match a filter -> Option D

4. Quick Check:

   updateMany updates multiple documents = C [OK]

Hint: updateMany changes many documents matching filter [OK]

Common Mistakes:

• Confusing updateMany with deleteMany
• Thinking updateMany inserts documents
• Believing updateMany finds documents

2. Which of the following is the correct syntax to update the field status to active for all documents where age is greater than 30 using updateMany?

easy

A. db.collection.updateMany({age: {$gt: 30}}, {$set: {status: 'active'}})

B. db.collection.updateMany({age: > 30}, {status: 'active'})

C. db.collection.updateMany({age: {$gt: 30}}, {status: 'active'})

D. db.collection.updateMany({age: {$gt: 30}}, {$update: {status: 'active'}})

Solution

1. Step 1: Check filter syntax

   The filter must use MongoDB query operators like $gt inside an object: {age: {$gt: 30}}.

2. Step 2: Check update operator

   The update must use an operator like $set to change fields: {$set: {status: 'active'}}.

3. Final Answer:

   db.collection.updateMany({age: {$gt: 30}}, {$set: {status: 'active'}}) -> Option A

4. Quick Check:

   Use $gt in filter and $set in update = A [OK]

Hint: Use $set to update fields, $gt for greater than in filter [OK]

Common Mistakes:

• Omitting $set operator in update
• Using invalid filter syntax like age: > 30
• Using $update instead of $set

3. Given the collection users with documents:

{"name": "Alice", "score": 50}, {"name": "Bob", "score": 40}, {"name": "Carol", "score": 50}

What will be the result of this command?

db.users.updateMany({score: 50}, {$inc: {score: 10}})

medium

A. One document updated, score becomes 60 for Alice only

B. No documents updated because $inc is invalid here

C. Two documents updated, scores become 60 for Alice and Carol

D. All documents updated, scores become 60, 50, 60

Solution

1. Step 1: Identify matching documents

   The filter {score: 50} matches Alice and Carol only.

2. Step 2: Understand the update operation

   The $inc operator increases the score field by 10 for each matched document.

3. Final Answer:

   Two documents updated, scores become 60 for Alice and Carol -> Option C

4. Quick Check:

   Filter matches 2 docs, $inc adds 10 = B [OK]

Hint: Filter matches 2 docs, $inc adds 10 to each [OK]

Common Mistakes:

• Thinking $inc only updates one document
• Assuming $inc is invalid in updateMany
• Believing all documents update regardless of filter

4. What is wrong with this updateMany command?

db.products.updateMany({price: {$lt: 100}}, {price: 90})

medium

A. Missing update operator like $set in the update document

B. Filter syntax is incorrect, $lt should be $gt

C. updateMany cannot update numeric fields

D. The collection name is invalid

Solution

1. Step 1: Check the update document

   The update document {price: 90} lacks an update operator like $set. MongoDB requires operators to specify how to update fields.

2. Step 2: Validate filter and collection

   The filter {price: {$lt: 100}} is correct, and collection name products is valid.

3. Final Answer:

   Missing update operator like $set in the update document -> Option A

4. Quick Check:

   Update needs $set or similar operator = A [OK]

Hint: Always use $set or $inc in update document [OK]

Common Mistakes:

• Forgetting $set operator
• Changing filter operator incorrectly
• Assuming updateMany can't update numbers

5. You want to increase the stock by 5 for all products with category 'books' and set lastUpdated to the current date. Which updateMany command correctly does this in one operation?

hard

A. db.products.updateMany({category: 'books'}, {stock: {$inc: 5}, lastUpdated: new Date()})

B. db.products.updateMany({category: 'books'}, {$inc: {stock: 5}, $set: {lastUpdated: new Date()}})

C. db.products.updateMany({category: 'books'}, {$set: {stock: stock + 5, lastUpdated: new Date()}})

D. db.products.updateMany({category: 'books'}, {$inc: {stock: 5}, lastUpdated: new Date()})

Solution

1. Step 1: Use correct update operators together

   To update multiple fields differently, combine $inc and $set inside one update document: {$inc: {...}, $set: {...}}.

2. Step 2: Validate syntax for date and increment

   new Date() sets current date, and $inc: {stock: 5} increases stock by 5. This matches db.products.updateMany({category: 'books'}, {$inc: {stock: 5}, $set: {lastUpdated: new Date()}}).

3. Final Answer:

   db.products.updateMany({category: 'books'}, {$inc: {stock: 5}, $set: {lastUpdated: new Date()}}) -> Option B

4. Quick Check:

   Combine $inc and $set correctly = D [OK]

Hint: Combine $inc and $set in one update document [OK]

Common Mistakes:

• Placing fields outside update operators
• Trying to do math inside $set without $inc
• Using invalid syntax for date or increment