HardSQL challenge #224CALCULATIONORDER BYANALYSIS

Sort Products by Profit Margin (Price Minus Cost)

Return every product with its margin, the price minus the cost, largest margin first.

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 with highest (price-cost) margin.

A correct answer returns 120 rows with 11 columns: id, name, category, price, cost, stock, sku, status, rating, review_count, margin.

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	margin
108	Succulent Plant Set	Home & Garden	1990.16	616.95	107	SKU-000108	discontinued	4	224	1373.21
68	Single Origin Coffee 500g	Food & Beverage	1991.75	657.28	195	SKU-000068	active	4.7	131	1334.47
28	Japanese Green Tea 50 bags	Food & Beverage	1937.51	620	488	SKU-000028	active	2.7	5	1317.51
65	Waterproof Hiking Boots	Sports & Outdoors	1769.01	566.08	164	SKU-000065	active	4.1	481	1202.9299999999998
1	Play Kitchen Deluxe	Toys	1786.38	589.51	257	SKU-000001	active	4	57	1196.8700000000001

First 5 of 120 rows. This is the output of the model solution on the practice database.

What you practise

Sorting the result with ORDER BY
Deriving a new column from an expression and naming it with an alias

Hint and approach

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

Show the hint

ORDER BY expression

Show the step-by-step approach

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

Read from the products table.
Add the calculated column margin: price - cost.
Sort the result by margin descending.

Model solution

Checking your session…

What to watch for

SQLite lets ORDER BY use the alias of a calculated column. WHERE cannot use it, because WHERE is evaluated before the SELECT list. This margin is in currency units; divide by price for a percentage.

Calculated columns. Dividing one integer by another truncates the result in SQLite. Multiply one side by 1.0 to get decimals.
ORDER BY. Without ORDER BY the row order is not guaranteed, even if it looks stable. Rows that tie on the sort columns can come back in any order.