SolveWithSQL

Difficulty: Beginner → Early Intermediate
Estimated time: 15–20 minutes
SQL concepts: SUM(), GROUP BY, ORDER BY, LIMIT
Goal: Return only the top N groups based on an aggregated metric.

The Challenge

The product manager asks:

“Which are our top 3 product categories by total value?”

This is a classic prioritization question used in:

• dashboards
• business reviews
• inventory decisions
• category performance reporting

To answer it, you must:

1. Aggregate totals per category
2. Sort totals from highest to lowest
3. Return only the top 3

Database Table

products

column_name	type	description
product_id	INTEGER	Unique product ID
name	TEXT	Product name
category	TEXT	Product category
price	DECIMAL	Product price

Sample Data

product_id	name	category	price
101	Wireless Mouse	Accessories	24.99
102	Mechanical Keyboard	Accessories	89.00
103	Webcam	Accessories	59.99
104	Monitor	Displays	229.99
105	USB-C Hub	Accessories	34.50
106	Laptop Stand	Workspace	39.99
107	Docking Station	Accessories	129.00
108	Chair Mat	Workspace	79.99
109	34-inch Monitor	Displays	399.00

Your Task

Write a SQL query that returns:

• Each category
• The total value of products in that category
• Sorted from highest to lowest total value
• Only the top 3 categories

Expected Output

category	total_value
Displays	628.99
Accessories	337.48
Workspace	119.98

(Exact totals depend on data; the Top-3 logic is the goal.)

Constraints

• Use SUM()
• Use GROUP BY
• Use ORDER BY on the aggregated total
• Use LIMIT to return only the top results
• Do not use SELECT *

Hint (Optional)

The correct order is:

1. GROUP BY
2. aggregate (e.g., SUM)
3. ORDER BY
4. LIMIT

If you apply LIMIT without sorting, you won’t get the “top” results.

Explanation

• GROUP BY category creates one row per category
• SUM(price) calculates total value per category
• ORDER BY total_value DESC ranks categories from highest to lowest total
• LIMIT 3 keeps only the top 3 categories

This is one of the most common patterns in analytics.

Key Insight

Top-N reporting is just: Aggregate → Sort → Limit

Once learners can do this, they can answer many “what matters most?” business questions.

Common Mistakes

• Forgetting DESC and ranking lowest totals first
• Using LIMIT without ORDER BY
• Ordering by price instead of SUM(price)

Optional Extension (Mini Bonus)

Try these variations:

1. Show the top 1 category only
2. Show the top 3 categories by average price
3. Show the bottom 3 categories (lowest total value)

🔗 Next Challenge

Beginner Challenge #30: Top-N with Ties (Handling Equal Totals)

Why this challenge matters

This is a direct bridge to real dashboards, where leaders ask:

“What are the top performers?”

Top-N queries are everywhere—and now your learners can write them.

🔗 View reference solution on GitHub
(After you’ve tried the challenge)

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