Comparison expressions ($eq, $gt in aggregation) in MongoDB - Mini Project: Build & Apply

Filtering Products with Comparison Expressions in MongoDB Aggregation

📖 Scenario: You are managing a small online store's product database. You want to find products based on their price and stock availability using MongoDB aggregation queries.

🎯 Goal: Build a MongoDB aggregation pipeline that filters products using comparison expressions $eq and $gt to find products with specific price and stock conditions.

📋 What You'll Learn

Create a collection named products with given product documents

Add a variable to specify the minimum stock threshold

Write an aggregation pipeline using $match with $eq and $gt comparison expressions

Complete the pipeline to return only products that meet the price and stock criteria

💡 Why This Matters

🌍 Real World

Filtering products in an online store database to find items matching specific price and stock conditions.

💼 Career

Understanding MongoDB aggregation with comparison expressions is essential for backend developers and data analysts working with NoSQL databases.

1

Create the products collection with sample data

Create a MongoDB collection called products and insert these exact documents: { name: "Pen", price: 5, stock: 50 }, { name: "Notebook", price: 15, stock: 20 }, { name: "Eraser", price: 3, stock: 100 }, { name: "Backpack", price: 45, stock: 10 }.

MongoDB

// Insert the products documents into the products collection
// Your code here

Need a hint?

Use db.products.insertMany([...]) with the exact product documents.

2

Set a minimum stock threshold variable

Create a variable called minStock and set it to 20 to use as the minimum stock threshold for filtering products.

MongoDB

db.products.insertMany([
  { name: "Pen", price: 5, stock: 50 },
  { name: "Notebook", price: 15, stock: 20 },
  { name: "Eraser", price: 3, stock: 100 },
  { name: "Backpack", price: 45, stock: 10 }
])

// Create minStock variable
// Your code here

Need a hint?

Use const minStock = 20 to define the threshold.

3

Write an aggregation pipeline using $eq and $gt

Create a variable called pipeline that contains an aggregation pipeline with a $match stage. Use $eq to filter products where price equals 15 and $gt to filter products where stock is greater than minStock.

MongoDB

db.products.insertMany([
  { name: "Pen", price: 5, stock: 50 },
  { name: "Notebook", price: 15, stock: 20 },
  { name: "Eraser", price: 3, stock: 100 },
  { name: "Backpack", price: 45, stock: 10 }
])

const minStock = 20

// Create pipeline variable with $match using $eq and $gt
// Your code here

Need a hint?

Use { $match: { price: { $eq: 15 }, stock: { $gt: minStock } } } inside the pipeline array.

4

Complete the aggregation query to find matching products

Use db.products.aggregate(pipeline) to run the aggregation pipeline and assign the result to a variable called result.

MongoDB

db.products.insertMany([
  { name: "Pen", price: 5, stock: 50 },
  { name: "Notebook", price: 15, stock: 20 },
  { name: "Eraser", price: 3, stock: 100 },
  { name: "Backpack", price: 45, stock: 10 }
])

const minStock = 20

const pipeline = [
  { $match: { price: { $eq: 15 }, stock: { $gt: minStock } } }
]

// Run the aggregation and assign to result
// Your code here

Need a hint?

Use const result = db.products.aggregate(pipeline) to run the query.