$gt and $gte for greater than in MongoDB - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ query_result

intermediate

Find documents with age greater than 30

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

MongoDB

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

A Returns all users with age less than or equal to 30

B Returns all users with age greater than or equal to 30

C Returns all users with age less than 30

D Returns all users with age strictly greater than 30

💡 Hint

Remember, $gt means strictly greater than, not including the value.

The $gt operator selects documents where the value of the field is strictly greater than the specified value. So { age: { $gt: 30 } } returns users older than 30, not including 30.

❓ query_result

intermediate

Find documents with age greater than or equal to 30

Which MongoDB query returns all users with age 30 or older?

MongoDB

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

A Returns users with age greater than or equal to 30

B Returns users with age strictly greater than 30

C Returns users with age less than 30

D Returns users with age less than or equal to 30

💡 Hint

Think about including the value 30 itself.

The $gte operator selects documents where the field value is greater than or equal to the specified value. So { age: { $gte: 30 } } includes users who are exactly 30 years old as well as older.

🧠 Conceptual

advanced

Difference between $gt and $gte

Which statement correctly describes the difference between $gt and $gte in MongoDB queries?

A <code>$gt</code> excludes the value specified, <code>$gte</code> includes it

B <code>$gt</code> includes the value specified, <code>$gte</code> excludes it

C Both <code>$gt</code> and <code>$gte</code> exclude the value specified

D Both <code>$gt</code> and <code>$gte</code> include the value specified

💡 Hint

Think about whether the boundary value is included or not.

$gt means strictly greater than, so it excludes the boundary value. $gte means greater than or equal to, so it includes the boundary value.

📝 Syntax

advanced

Identify the valid MongoDB query syntax for greater than

Which of the following MongoDB queries is syntactically correct to find documents where score is greater than 50?

A db.collection.find({ score > 50 })

B db.collection.find({ score: $gt 50 })

C db.collection.find({ score: { $gt: 50 } })

D db.collection.find({ score: { gt: 50 } })

💡 Hint

Remember the syntax for operators in MongoDB queries uses $ and colon.

The correct syntax uses { field: { $operator: value } }. Option C follows this pattern. Options B, C, and D are invalid syntax.

❓ optimization

expert

Optimizing queries using $gt and $gte with indexes

You have a large collection with an index on the price field. Which query will best use the index to find documents with price greater than or equal to 100?

A db.products.find({ price: { $gt: 99 } })

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

C db.products.find({ price: { $gte: 100 }, price: { $lt: 200 } })

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

💡 Hint

Think about the exact boundary value and index usage.

Option B directly queries for price >= 100, which matches the index efficiently. Option B uses $gt 99 which is equivalent but less clear. Option B adds an upper bound which may be useful but is not asked. Option B excludes 100, so it misses some documents.

Practice

1. What does the $gt operator do in a MongoDB query?

easy

A. Finds documents where the field value is less than the specified value.

B. Finds documents where the field value is equal to the specified value.

C. Finds documents where the field value is strictly greater than the specified value.

D. Finds documents where the field value is greater than or equal to the specified value.

Solution

1. Step 1: Understand the meaning of $gt

   The $gt operator means "greater than" and selects values strictly larger than the given number.

2. Step 2: Compare with other operators

   $gte means "greater than or equal to", so it includes the number itself, unlike $gt.

3. Final Answer:

   Finds documents where the field value is strictly greater than the specified value. -> Option C

4. Quick Check:

   $gt = strictly greater than [OK]

Hint: Remember: $gt means strictly greater than [OK]

Common Mistakes:

• Confusing $gt with $gte
• Thinking $gt includes equal values
• Mixing $gt with less than operators

2. Which of the following is the correct syntax to find documents where the field age is greater than or equal to 18 in MongoDB?

easy

A. { age: { $gte: 18 } }

B. { age: { $gt: 18 } }

C. { age: { $gte: "18" } }

D. { age: { $gte: > 18 } }

Solution

1. Step 1: Check the operator and syntax

   The correct operator for "greater than or equal to" is $gte, and it must be used as { field: { $gte: value } }.

2. Step 2: Validate the value type and format

   The value should be a number (18), not a string or invalid syntax like > 18.

3. Final Answer:

   { age: { $gte: 18 } } -> Option A

4. Quick Check:

   Correct syntax uses $gte with number [OK]

Hint: Use { field: { $gte: number } } for greater or equal [OK]

Common Mistakes:

• Using quotes around numbers
• Writing invalid syntax like $gte: > 18
• Confusing $gt and $gte

3. Given the collection products with documents:

{ "name": "Pen", "price": 5 }

{ "name": "Notebook", "price": 10 }

{ "name": "Backpack", "price": 20 }

What will be the result of the query db.products.find({ price: { $gt: 10 } })?

medium

A. [{ "name": "Notebook", "price": 10 }, { "name": "Backpack", "price": 20 }]

B. [{ "name": "Pen", "price": 5 }]

C. []

D. [{ "name": "Backpack", "price": 20 }]

Solution

1. Step 1: Understand the query condition

   The query uses $gt: 10, so it selects documents where price is strictly greater than 10.

2. Step 2: Check each document's price

   "Pen" has price 5 (not > 10), "Notebook" has price 10 (not > 10), "Backpack" has price 20 (greater than 10).

3. Final Answer:

   [{ "name": "Backpack", "price": 20 }] -> Option D

4. Quick Check:

   Only price > 10 matches [OK]

Hint: Remember $gt excludes equal values [OK]

Common Mistakes:

• Including documents with price equal to 10
• Confusing $gt with $gte
• Selecting documents with price less than 10

4. You wrote the query db.users.find({ age: { $gte: 21 } }) but it returns no results even though some users are 21 or older. What is the likely problem?

medium

A. You should use $gt instead of $gte.

B. The field name age is misspelled in the documents.

C. The query syntax is incorrect; $gte cannot be used here.

D. MongoDB does not support $gte operator.

Solution

1. Step 1: Check the query syntax

   The syntax { age: { $gte: 21 } } is correct and supported by MongoDB.

2. Step 2: Consider data issues

   If no results appear, likely the field age is misspelled or missing in documents, so no matches occur.

3. Final Answer:

   The field name age is misspelled in the documents. -> Option B

4. Quick Check:

   Field name mismatch causes no results [OK]

Hint: Check field names carefully if no results [OK]

Common Mistakes:

• Assuming $gte is unsupported
• Switching $gte to $gt unnecessarily
• Ignoring possible typos in field names

5. You want to find all orders with a total amount greater than or equal to 100 but less than 200. Which MongoDB query correctly uses $gte and $gt to achieve this?

hard

A. { total: { $gte: 100, $lt: 200 } }

B. { total: { $gt: 100, $gte: 200 } }

C. { total: { $gte: 100, $gt: 200 } }

D. { total: { $gte: 100, $gt: 199 } }

Solution

1. Step 1: Understand the range conditions

   You want totals >= 100 and < 200, so use $gte: 100 and $lt: 200 (less than 200).

2. Step 2: Check each option's operators

   { total: { $gte: 100, $lt: 200 } } correctly uses $gte: 100 and $lt: 200. Other options misuse operators or values.

3. Final Answer:

   { total: { $gte: 100, $lt: 200 } } -> Option A

4. Quick Check:

   Use $gte for lower bound, $lt for upper bound [OK]

Hint: Use $gte for start, $lt for end of range [OK]

Common Mistakes:

• Using $gt instead of $gte for lower bound
• Using $gte for upper bound instead of $lt
• Mixing operator directions incorrectly