EasySQL challenge #86WHERE

Compare Two Columns in a WHERE Clause

Return the products whose cost is lower than their selling price.

The challenge runs on the SQLabHub practice database (SQLite) and uses the products table. You can solve it in the browser, with nothing to install.

Solve This SQL Challenge

The task

Find products where cost is less than price.

A correct answer returns 120 rows with 10 columns: id, name, category, price, cost, stock, sku, status, rating, review_count.

Tables used in this challenge

`products` 120 rows

id INTEGER (PK) · name TEXT · category TEXT · price REAL · cost REAL · stock INTEGER · sku TEXT · status TEXT · rating REAL · review_count INTEGER

First 3 rows of the products table
id	name	category	price	cost	stock	sku	status	rating	review_count
1	Play Kitchen Deluxe	Toys	1786.38	589.51	257	SKU-000001	active	4	57
2	Micro-Cut Paper Shredder 8-Sheet	Office Supplies	907.93	281.46	131	SKU-000002	active	2.5	447
3	4K Dual Dash Camera	Automotive	568.89	204.8	176	SKU-000003	active	4.1	29

The first rows of each table are shown. See how all the tables relate on the database schema page.

Expected output

Expected output of the challenge
id	name	category	price	cost	stock	sku	status	rating	review_count
1	Play Kitchen Deluxe	Toys	1786.38	589.51	257	SKU-000001	active	4	57
2	Micro-Cut Paper Shredder 8-Sheet	Office Supplies	907.93	281.46	131	SKU-000002	active	2.5	447
3	4K Dual Dash Camera	Automotive	568.89	204.8	176	SKU-000003	active	4.1	29
4	Ergonomic Desk Mat XL	Office Supplies	1618.64	663.64	164	SKU-000004	active	4	262
5	Premium Beard Oil 60ml	Health & Beauty	1428.31	428.49	183	SKU-000005	active	5	305

First 5 of 120 rows. This is the output of the model solution on the practice database. The task does not fix a sort order, so your rows may come back in a different order.

What you practise

Returning every column of a table with SELECT *
Filtering rows with a WHERE condition

Hint and approach

Try the challenge first. Open these only when you need them.

Show the hint

Compare two columns

Show the step-by-step approach

How the model solution is built, in the order the database evaluates it:

Read from the products table.
Filter in WHERE: keep the rows where cost is less than price.
Return every column with SELECT *.

Model solution

Checking your session…

What to watch for

Either side of a comparison can be a column, so each row is tested against its own values. Every product in this dataset is sold above cost, so all of them are returned; reversing the operator is the useful data-quality check.

WHERE. WHERE is evaluated before the SELECT list, so it cannot use a column alias defined there or the result of an aggregate.
SELECT *. SELECT * is fine for exploring, but its output changes whenever a column is added to the table. Queries that feed a report should name their columns.