updateOne method in MongoDB - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ query_result

intermediate

What does this updateOne query do?

Consider a MongoDB collection named users with documents containing name and age. What will be the result of this query?

db.users.updateOne({ name: "Alice" }, { $set: { age: 30 } })

MongoDB

db.users.updateOne({ name: "Alice" }, { $set: { age: 30 } })

A Updates all documents where name is 'Alice' by setting age to 30

B Updates the first document where name is 'Alice' by setting age to 30

C Inserts a new document with name 'Alice' and age 30 if none exists

D Deletes the first document where name is 'Alice'

💡 Hint

Remember, updateOne affects only one matching document.

The updateOne method updates only the first document matching the filter. It sets the age field to 30 for the first user named 'Alice'. It does not update multiple documents or insert new ones.

📝 Syntax

intermediate

Which updateOne query is syntactically correct?

Choose the correct syntax for updating the status field to 'active' for the user with userId 123.

A db.users.updateOne({ userId: 123 }, { status: 'active' })

B db.users.updateOne({ userId: 123 }, { set: { status: 'active' } })

C db.users.updateOne({ userId: 123 }, { $update: { status: 'active' } })

D db.users.updateOne({ userId: 123 }, { $set: { status: 'active' } })

💡 Hint

Use the correct update operator to modify fields.

The $set operator is required to update specific fields in a document. Options A, B, and D either miss the operator or use incorrect ones.

❓ optimization

advanced

Optimizing updateOne with upsert option

You want to update the score of a player with playerId 42. If no such player exists, insert a new document with playerId 42 and score 100. Which query achieves this efficiently?

A db.players.updateOne({ playerId: 42 }, { $set: { score: 100 } }, { upsert: true })

B db.players.updateMany({ playerId: 42 }, { $set: { score: 100 } }, { upsert: true })

C db.players.insertOne({ playerId: 42, score: 100 })

D db.players.updateOne({ playerId: 42 }, { $set: { score: 100 } })

💡 Hint

Use the option that inserts if no match is found.

The upsert option in updateOne inserts a new document if no matching document exists. updateMany is not needed here, and insertOne does not update existing documents.

🔧 Debug

advanced

Why does this updateOne query fail?

Given the query:

db.orders.updateOne({ orderId: 101 }, { status: 'shipped' })

It does not update the document as expected. What is the cause?

A Missing $set operator in the update document

B orderId field does not exist in the collection

C updateOne cannot update string fields

D The filter object is empty

💡 Hint

Check the update document structure.

The update document must use an update operator like $set. Without it, MongoDB treats the document as a replacement, which is invalid here.

🧠 Conceptual

expert

What is the difference between updateOne and findOneAndUpdate?

Which statement correctly describes a key difference between updateOne and findOneAndUpdate methods in MongoDB?

A updateOne returns the updated document, findOneAndUpdate returns only the update result

B Both methods behave identically in all cases

C findOneAndUpdate returns the original or updated document, updateOne returns only update status

D updateOne updates multiple documents, findOneAndUpdate updates only one

💡 Hint

Consider what each method returns after updating.

updateOne returns a result object with status info but not the document. findOneAndUpdate returns the document before or after update depending on options.