Challenge 1: Select Specific Columns (Without Overfetching)

Difficulty: Beginner
Estimated time: 5–10 minutes
SQL concepts: SELECT, choosing columns, result sets
Goal: Retrieve only the columns you need (a core real-world SQL habit).

The Scenario

You’re working with an e-commerce database. A product manager asks for a simple list of products showing:

Product name
Price
Category

They do not want internal columns like IDs, created timestamps, or inventory details.

Your task is to write a query that returns only the requested columns.

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
stock_qty	INTEGER	Units in stock
created_at	TIMESTAMP	When the product was created

Sample Data (for context)

product_id	name	category	price	stock_qty	created_at
101	Wireless Mouse	Accessories	24.99	120	2025-01-10 09:00:00
102	Mechanical Keyboard	Accessories	89.00	45	2025-01-12 10:30:00
103	27-inch Monitor	Displays	229.99	18	2025-01-15 12:20:00
104	USB-C Hub	Accessories	34.50	70	2025-01-18 14:00:00
105	Laptop Stand	Workspace	39.99	32	2025-01-21 16:10:00

Your Task

Write a SQL query that returns:

name
price
category

From the products table.

Expected Output

Your result should look like this:

name	price	category
Wireless Mouse	24.99	Accessories
Mechanical Keyboard	89.00	Accessories
27-inch Monitor	229.99	Displays
USB-C Hub	34.50	Accessories
Laptop Stand	39.99	Workspace

Constraints

Do not use SELECT *
Return only the three requested columns
The column order should be: name, price, category

Hint (Optional)

In SQL, you specify the columns you want right after SELECT, separated by commas.

SELECT name, price, category FROM products;

Explanation

SELECT name, price, category tells the database exactly which columns to return.
FROM products tells it which table to read from.
This avoids pulling unnecessary data, which is more efficient and is best practice in production SQL.

Common Mistakes

Using SELECT *
- Works, but returns extra columns you didn’t ask for (and often slows real systems).
Wrong column order
- Many automated checkers and dashboards expect a specific ordering.
Misspelling column names
- SQL will error if category is typed incorrectly.

Optional Extension (Mini Bonus)

Modify your query to return only products where the category is Accessories.

(You’ll learn WHERE in Challenge #2, but it’s fine to try.)

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