Finding and querying documents in Express - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of the find() method in Express when working with databases?

The find() method is used to search for multiple documents in a database collection that match given criteria. It returns all matching documents as an array.

beginner

How do you query documents with a specific field value using Express and MongoDB?

You pass an object with the field and value to find(). For example, Model.find({ age: 25 }) finds all documents where the age field equals 25.

beginner

What does findOne() do differently from find()?

findOne() returns only the first document that matches the query criteria, instead of all matching documents.

intermediate

How can you limit the number of documents returned in a query?

You can chain the limit() method after find() to restrict how many documents are returned. For example, Model.find().limit(5) returns only 5 documents.

beginner

What is the role of the callback or promise in querying documents with Express?

The callback or promise handles the asynchronous result of the query. It lets you access the found documents once the database finishes searching.

Which method returns all documents matching a query in Express?

A save()

B findOne()

C find()

D update()

find() returns all matching documents, while findOne() returns only one.

How do you find documents where the field 'status' equals 'active'?

A Model.find({ status })

B Model.findOne('active')

C Model.find({ 'active': status })

D Model.find({ status: 'active' })

You pass an object with the field and value: { status: 'active' }.

What does limit(3) do when chained after find()?

A Returns only 3 documents

B Skips 3 documents

C Sorts documents by 3 fields

D Deletes 3 documents

limit(3) restricts the result to 3 documents.

Which method returns only the first matching document?

A findOne()

B find()

C updateOne()

D deleteOne()

findOne() returns the first document matching the query.

Why do queries in Express often use callbacks or promises?

A To format the output

B Because database operations are asynchronous

C To speed up the query

D To block the main thread

Database queries take time, so callbacks or promises handle results when ready without blocking.

Explain how to find documents with a specific field value using Express.

Think about how you tell the database what to look for.

Describe the difference between find() and findOne() methods.

One returns many, the other returns one.