sort method ascending and descending in MongoDB - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ query_result

intermediate

Sort documents by age ascending

Given a collection users with documents containing name and age, what is the output of this query?

db.users.find().sort({age: 1})

Assume the collection has:
{name: 'Alice', age: 30}
{name: 'Bob', age: 25}
{name: 'Carol', age: 35}

MongoDB

db.users.find().sort({age: 1})

A [{name: 'Bob', age: 25}, {name: 'Alice', age: 30}, {name: 'Carol', age: 35}]

B [{name: 'Carol', age: 35}, {name: 'Alice', age: 30}, {name: 'Bob', age: 25}]

C [{name: 'Alice', age: 30}, {name: 'Bob', age: 25}, {name: 'Carol', age: 35}]

D [{name: 'Bob', age: 25}, {name: 'Carol', age: 35}, {name: 'Alice', age: 30}]

💡 Hint

Sorting by age with 1 means ascending order.

The sort method with {age: 1} sorts documents by age from smallest to largest.

❓ query_result

intermediate

Sort documents by age descending

Using the same users collection, what is the output of this query?

db.users.find().sort({age: -1})

With documents:
{name: 'Alice', age: 30}
{name: 'Bob', age: 25}
{name: 'Carol', age: 35}

MongoDB

db.users.find().sort({age: -1})

A [{name: 'Bob', age: 25}, {name: 'Alice', age: 30}, {name: 'Carol', age: 35}]

B [{name: 'Alice', age: 30}, {name: 'Carol', age: 35}, {name: 'Bob', age: 25}]

C [{name: 'Carol', age: 35}, {name: 'Bob', age: 25}, {name: 'Alice', age: 30}]

D [{name: 'Carol', age: 35}, {name: 'Alice', age: 30}, {name: 'Bob', age: 25}]

💡 Hint

Sorting by age with -1 means descending order.

The sort method with {age: -1} sorts documents by age from largest to smallest.

🧠 Conceptual

advanced

Understanding sort order values

In MongoDB, what do the values 1 and -1 mean when used in the sort() method?

A 1 means ascending order, -1 means descending order

B 1 means descending order, -1 means ascending order

C 1 means sort by string length, -1 means sort by numeric value

D 1 means no sorting, -1 means reverse sorting

💡 Hint

Think about smallest to largest and largest to smallest.

In MongoDB, 1 sorts ascending (smallest to largest), -1 sorts descending (largest to smallest).

📝 Syntax

advanced

Identify the invalid sort syntax

Which of the following MongoDB sort method calls will cause a syntax error?

A db.collection.find().sort({age: 1})

B db.collection.find().sort({age: -1})

C db.collection.find().sort({age: 'asc'})

D db.collection.find().sort({age: 0})

💡 Hint

Sort values must be numeric 1 or -1.

MongoDB sort values must be 1 or -1. Using 'asc' as a string causes an error.

❓ optimization

expert

Optimizing sort with index

You have a large MongoDB collection with an index on age. Which query will use the index efficiently for sorting by age descending?

A db.collection.find().sort({age: 0})

B db.collection.find().sort({age: -1})

C db.collection.find().sort({name: 1})

D db.collection.find().sort({age: 1})

💡 Hint

Index on age supports sorting by age ascending or descending.

Sorting by age descending matches the index on age and uses it efficiently.