find method basics in MongoDB - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ query_result

intermediate

Find documents with a specific field value

Given a collection users with documents containing age and name, what does the following query return?

db.users.find({ age: 25 })

MongoDB

db.users.find({ age: 25 })

A An error because the query syntax is invalid

B All documents where the age field is greater than 25

C All documents where the name field is '25'

D All documents where the age field is exactly 25

💡 Hint

Think about what the object inside find() means.

The find method with { age: 25 } returns all documents where the age field equals 25 exactly.

📝 Syntax

intermediate

Identify the syntax error in a find query

Which option contains a syntax error in the MongoDB find method?

MongoDB

db.products.find({ price: { $gt: 100 } })

A db.products.find({ price: { $gt: 100 } })

B db.products.find({ price: $gt: 100 })

C db.products.find({ price: { $lt: 50 } })

D db.products.find({ price: { $eq: 75 } })

💡 Hint

Look for missing or misplaced braces and colons.

Option B is missing braces around the $gt operator, causing a syntax error.

❓ query_result

advanced

Find documents with multiple conditions

What documents does this query return?

db.orders.find({ status: 'shipped', quantity: { $gte: 10 } })

MongoDB

db.orders.find({ status: 'shipped', quantity: { $gte: 10 } })

A Documents where quantity is at least 10 only

B Documents where status is 'shipped' or quantity is at least 10

C Documents where status is 'shipped' and quantity is at least 10

D Documents where status is 'shipped' and quantity is exactly 10

💡 Hint

Multiple fields in the query object mean AND condition.

MongoDB find with multiple fields matches documents where all conditions are true (AND).

🔧 Debug

advanced

Why does this find query return no results?

A collection employees has documents with a field department. The query below returns no documents, but you expect some.

db.employees.find({ department: 'Sales' })

What is the most likely reason?

A The field name is case-sensitive and the actual field is 'Department' with capital D

B The collection is empty

C The query syntax is invalid and causes an error

D The database connection is lost

💡 Hint

Check exact spelling and case of field names in documents.

MongoDB field names are case-sensitive. If the field is 'Department', querying 'department' returns no matches.

🧠 Conceptual

expert

Understanding find method cursor behavior

What does the find() method return in MongoDB when called without toArray() or iteration?

A A cursor object that points to the matching documents but does not fetch them immediately

B An array of all matching documents immediately

C A single document matching the query

D An error because find() must be followed by toArray()

💡 Hint

Think about how MongoDB handles large result sets efficiently.

The find() method returns a cursor, which is a pointer to the result set. Documents are fetched as needed.