MongoDB Aggregation Practice Challenges with Solutions (Part - 5)

🧩 MongoDB Practice Series – Aggregation Challenges with Solutions (Part 5)

← Part 4 MongoDB Tutorial Next →

Welcome to Part 5 of the MongoDB Practice Series.

In this lesson, you will practice Aggregation in MongoDB.

Aggregation helps you perform calculations like:

• Total
• Average
• Count
• Grouping data

These skills are very useful for reports and analytics.

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🟢 Exercise 1: Count Total Documents

Problem:
Count the total number of students in the collection.

Solution:

db.students.countDocuments()

Learning Goal: Learn how to count records.

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🟡 Exercise 2: Calculate Average Value

Problem:
Find the average price of all products.

Solution:

db.products.aggregate([
  {
    $group: {
      _id: null,
      averagePrice: { $avg: "$price" }
    }
  }
])

Learning Goal: Use $group and $avg.

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🟡 Exercise 3: Calculate Total Sum

Problem:
Find the total revenue from all orders.

Solution:

db.orders.aggregate([
  {
    $group: {
      _id: null,
      totalRevenue: { $sum: "$totalAmount" }
    }
  }
])

Learning Goal: Use $sum to calculate totals.

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🔵 Exercise 4: Group Data by Category

Problem:
Count how many products exist in each category.

Solution:

db.products.aggregate([
  {
    $group: {
      _id: "$category",
      totalProducts: { $sum: 1 }
    }
  }
])

Learning Goal: Understand grouping by field value.

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🔵 Exercise 5: Find Maximum Value

Problem:
Find the highest product price.

Solution:

db.products.aggregate([
  {
    $group: {
      _id: null,
      highestPrice: { $max: "$price" }
    }
  }
])

Learning Goal: Use $max.

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🔴 Exercise 6: Group and Filter Results

Problem:
Find categories that have more than 5 products.

Solution:

db.products.aggregate([
  {
    $group: {
      _id: "$category",
      count: { $sum: 1 }
    }
  },
  {
    $match: {
      count: { $gt: 5 }
    }
  }
])

Learning Goal: Combine $group with $match.

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🚀 Mini Challenge

Create a collection called sales with fields:

• productName
• category
• quantity
• price

Then write queries to:

• Calculate total revenue (quantity × price)
• Find total sales per category
• Find the category with highest total sales

Try solving step by step.

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🎯 What’s Next?

In Part 6 of the MongoDB Practice Series, we will practice:

• Real-world schema design scenarios
• Embedding vs referencing decisions
• Designing scalable databases

Stay tuned for the next level!

← Part 4 MongoDB Tutorial Next →

MongoDB Sorting, Limiting & Pagination Practice Exercises (Part-4)

🧩 MongoDB Practice Series – Sorting, Limiting & Pagination Exercises (Part 4)

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Welcome to Part 4 of the MongoDB Practice Series.

In this lesson, you will practice:

• Sorting data
• Limiting results
• Using skip for pagination
• Combining filters with sorting

These skills are very important in real-world applications like websites and dashboards.

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🟢 Exercise 1: Sort in Ascending Order

Problem:
Retrieve all students and sort them by age in ascending order.

Solution:

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

Learning Goal: Use 1 for ascending order.

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🟢 Exercise 2: Sort in Descending Order

Problem:
Retrieve all products and sort them by price from highest to lowest.

Solution:

db.products.find().sort({ price: -1 })

Learning Goal: Use -1 for descending order.

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🟡 Exercise 3: Limit Results

Problem:
Show only the top 3 highest-priced products.

Solution:

db.products.find().sort({ price: -1 }).limit(3)

Learning Goal: Combine sorting with limiting.

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🟡 Exercise 4: Pagination Using Skip

Problem:
Display the second page of results where each page shows 5 records.

Solution:

db.students.find()
  .skip(5)
  .limit(5)

Learning Goal: Understand basic pagination.

Explanation:
- skip(5) skips the first 5 records.
- limit(5) shows the next 5 records.

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🔵 Exercise 5: Filter + Sort

Problem:
Find students with age greater than 18 and sort them by name in alphabetical order.

Solution:

db.students.find({
  age: { $gt: 18 }
}).sort({ name: 1 })

Learning Goal: Combine filtering with sorting.

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🔵 Exercise 6: Get Latest Records

Problem:
Assume each document has a field called createdAt. Retrieve the 5 most recently added documents.

Solution:

db.posts.find()
  .sort({ createdAt: -1 })
  .limit(5)

Learning Goal: This pattern is commonly used in blogs and news websites.

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🔴 Exercise 7: Complex Real-World Scenario

Problem:
From the products collection:

• Find products where price is greater than 1000
• Sort them by price (highest first)
• Show only top 2 results

Solution:

db.products.find({
  price: { $gt: 1000 }
})
.sort({ price: -1 })
.limit(2)

Learning Goal: Practice combining multiple concepts in one query.

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🚀 Mini Challenge

Create a collection called orders with fields:

• orderId
• customerName
• totalAmount
• orderDate

Then write queries to:

• Show the latest 5 orders
• Sort orders by totalAmount (highest first)
• Display page 2 if each page contains 3 orders

Try solving without looking back at the examples.

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🎯 What’s Next?

In Part 5 of the MongoDB Practice Series, we will practice:

• Aggregation challenges
• $group operations
• Calculating totals and averages
• Real-world reporting queries

Stay tuned for the next level!

← Part 3 MongoDB Tutorial Part 5 →