sort method ascending and descending in MongoDB - Mini Project: Build & Apply

Sorting Documents with MongoDB sort Method

📖 Scenario: You are managing a small online bookstore database. You want to organize the books so customers can see them sorted by price, either from cheapest to most expensive or the other way around.

🎯 Goal: Build MongoDB queries that use the sort method to display books sorted by their price in ascending and descending order.

📋 What You'll Learn

Create a collection named books with the exact documents provided.

Create a variable sortAscending that holds the sorting order for ascending by price.

Create a variable sortDescending that holds the sorting order for descending by price.

Write a query using find() and sort(sortAscending) to get books sorted by price ascending.

Write a query using find() and sort(sortDescending) to get books sorted by price descending.

💡 Why This Matters

🌍 Real World

Sorting data is essential in databases to help users find information quickly, like showing products from cheapest to most expensive.

💼 Career

Database developers and data analysts often write queries to sort data efficiently for reports and user interfaces.

1

Create the books collection with sample data

Create a variable called books that is an array of documents with these exact entries: { title: "Book A", price: 15 }, { title: "Book B", price: 10 }, { title: "Book C", price: 20 }.

MongoDB

// Create the books array with the specified documents
// Your code here

Hint

Use an array of objects with the exact titles and prices given.

2

Define sorting order variables

Create a variable called sortAscending and set it to { price: 1 }. Then create a variable called sortDescending and set it to { price: -1 }.

MongoDB

const books = [
  { title: "Book A", price: 15 },
  { title: "Book B", price: 10 },
  { title: "Book C", price: 20 }
];

// Define sortAscending and sortDescending variables
// Your code here

Hint

Use 1 for ascending and -1 for descending order in the sort object.

3

Write query to sort books by price ascending

Write a query called booksSortedAsc that uses books.find().sort(sortAscending) to get books sorted by price in ascending order.

MongoDB

const books = [
  { title: "Book A", price: 15 },
  { title: "Book B", price: 10 },
  { title: "Book C", price: 20 }
];

const sortAscending = { price: 1 };
const sortDescending = { price: -1 };

// Write the query booksSortedAsc using find() and sort(sortAscending)
// Your code here

Hint

Use JavaScript array sort method to sort the books by price ascending.

4

Write query to sort books by price descending

Write a query called booksSortedDesc that uses books.find().sort(sortDescending) to get books sorted by price in descending order.

MongoDB

const books = [
  { title: "Book A", price: 15 },
  { title: "Book B", price: 10 },
  { title: "Book C", price: 20 }
];

const sortAscending = { price: 1 };
const sortDescending = { price: -1 };

const booksSortedAsc = books.sort((a, b) => a.price - b.price);

// Write the query booksSortedDesc using sortDescending
// Your code here

Hint

Use JavaScript array sort method to sort the books by price descending.

Practice

1. What does the sort({ age: 1 }) method do in MongoDB?

easy

A. Deletes documents with age less than 1

B. Sorts documents by age in descending order (largest to smallest)

C. Filters documents where age equals 1

D. Sorts documents by age in ascending order (smallest to largest)

Solution

1. Step 1: Understand the sort method parameter

   The number 1 in sort({ age: 1 }) means ascending order.

2. Step 2: Interpret the sorting effect

   Documents will be arranged from smallest age to largest age.

3. Final Answer:

   Sorts documents by age in ascending order (smallest to largest) -> Option D

4. Quick Check:

   sort({ field: 1 }) = ascending order [OK]

Hint: 1 means ascending order, -1 means descending order [OK]

Common Mistakes:

• Confusing 1 with descending order
• Thinking sort filters data
• Assuming sort deletes documents

2. Which of the following is the correct syntax to sort documents by score in descending order in MongoDB?

easy

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

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

C. db.collection.find().sort(score: -1)

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

Solution

1. Step 1: Check the correct object syntax for sort

   The sort method requires an object with field name as key and 1 or -1 as value, inside curly braces.

2. Step 2: Identify descending order syntax

   Descending order is indicated by -1, so { score: -1 } is correct.

3. Final Answer:

   db.collection.find().sort({ score: -1 }) -> Option A

4. Quick Check:

   sort({ field: -1 }) = descending order [OK]

Hint: Use curly braces and colon: sort({ field: -1 }) [OK]

Common Mistakes:

• Missing curly braces around sort argument
• Using parentheses instead of braces
• Putting -1 as key instead of value

3. Given the documents: [{"name": "Anna", "score": 85}, {"name": "Ben", "score": 92}, {"name": "Cara", "score": 78}], what will be the order of names after running db.students.find().sort({ score: 1 })?

medium

A. ["Ben", "Anna", "Cara"]

B. ["Cara", "Ben", "Anna"]

C. ["Cara", "Anna", "Ben"]

D. ["Anna", "Cara", "Ben"]

Solution

1. Step 1: Understand ascending sort by score

   Sorting by score ascending means from smallest to largest score: 78, 85, 92.

2. Step 2: Map scores to names in order

   78 = Cara, 85 = Anna, 92 = Ben, so order is ["Cara", "Anna", "Ben"].

3. Final Answer:

   ["Cara", "Anna", "Ben"] -> Option C

4. Quick Check:

   sort({ score: 1 }) = ascending order [OK]

Hint: Ascending sort orders from smallest to largest [OK]

Common Mistakes:

• Mixing ascending with descending order
• Sorting by name instead of score
• Confusing array order in output

4. What is wrong with this MongoDB query?

db.products.find().sort({ price: 2 })

medium

A. The find() method cannot be chained with sort()

B. The sort value must be 1 or -1, not 2

C. The field name 'price' is invalid

D. Missing parentheses after sort

Solution

1. Step 1: Check valid sort values

   MongoDB sort only accepts 1 for ascending or -1 for descending, not 2.

2. Step 2: Identify the error cause

   Using 2 will cause a syntax or runtime error because it's invalid.

3. Final Answer:

   The sort value must be 1 or -1, not 2 -> Option B

4. Quick Check:

   sort values = 1 or -1 only [OK]

Hint: Sort values must be exactly 1 or -1 [OK]

Common Mistakes:

• Using numbers other than 1 or -1
• Assuming any positive number works
• Thinking sort can't chain after find()

5. You have a collection with documents containing category and price. How do you sort first by category ascending, then by price descending?

hard

A. db.collection.find().sort({ category: 1, price: -1 })

B. db.collection.find().sort({ price: -1, category: 1 })

C. db.collection.find().sort({ category: -1, price: 1 })

D. db.collection.find().sort({ category: 1 }).sort({ price: -1 })

Solution

1. Step 1: Understand multi-field sort syntax

   MongoDB sorts by fields in the order they appear in the object passed to sort().

2. Step 2: Apply ascending to category and descending to price

   Use { category: 1, price: -1 } to sort category ascending, then price descending within each category.

3. Final Answer:

   db.collection.find().sort({ category: 1, price: -1 }) -> Option A

4. Quick Check:

   Multi-field sort = object with fields in order [OK]

Hint: List fields in sort object in desired priority order [OK]

Common Mistakes:

• Reversing field order changes sort priority
• Trying to chain multiple sort() calls
• Using wrong sort values for fields