$lt and $lte for less than in MongoDB - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ query_result

intermediate

Find documents with age less than 30

Given a collection users with documents containing an age field, which query returns all users younger than 30?

MongoDB

db.users.find({ age: { $lt: 30 } })

A db.users.find({ age: { $gt: 30 } })

B db.users.find({ age: { $lte: 30 } })

C db.users.find({ age: { $lt: 30 } })

D db.users.find({ age: { $gte: 30 } })

💡 Hint

Remember, $lt means strictly less than, while $lte means less than or equal to.

The $lt operator selects documents where the value is strictly less than the specified number. Here, it returns users with age less than 30.

❓ query_result

intermediate

Find documents with price less than or equal to 100

Which query returns all products with a price less than or equal to 100?

MongoDB

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

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

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

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

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

💡 Hint

Check if the query includes products priced exactly at 100.

The $lte operator includes values less than or equal to the specified number, so products priced at 100 are included.

📝 Syntax

advanced

Identify the syntax error in this query

Which option contains a syntax error when trying to find documents with score less than 50?

MongoDB

db.scores.find({ score: { $lt 50 } })

A db.scores.find({ score: { $lt: '50' } })

B db.scores.find({ score: { $lt: 50 } })

C db.scores.find({ score: { $lte: 50 } })

D db.scores.find({ score: { $lt 50 } })

💡 Hint

Check the syntax for specifying operators and values in MongoDB queries.

Option D is missing the colon : between $lt and the value, causing a syntax error.

❓ query_result

advanced

Find documents with date less than or equal to a specific date

Given documents with a date field, which query returns all documents with date less than or equal to January 1, 2023?

MongoDB

db.events.find({ date: { $lte: new Date('2023-01-01') } })

A db.events.find({ date: { $lt: new Date('2023-01-01') } })

B db.events.find({ date: { $lte: new Date('2023-01-01') } })

C db.events.find({ date: { $gt: new Date('2023-01-01') } })

D db.events.find({ date: { $gte: new Date('2023-01-01') } })

💡 Hint

Remember that $lte includes the date itself.

The $lte operator includes documents where the date is exactly January 1, 2023, or earlier.

🧠 Conceptual

expert

Understanding difference between $lt and $lte in query results

If a collection items has documents with a numeric field value containing values 10, 20, 30, and 40, what is the number of documents returned by db.items.find({ value: { $lt: 30 } }) compared to db.items.find({ value: { $lte: 30 } })?

A The first query returns 2 documents; the second returns 3 documents

B Both queries return 2 documents

C The first query returns 3 documents; the second returns 2 documents

D Both queries return 3 documents

💡 Hint

Think about whether the value 30 is included in each query.

The $lt query returns documents with values less than 30 (10 and 20), so 2 documents. The $lte query includes 30 as well, so it returns 3 documents.