HardSQL challenge #337CALCULATIONORDER BYANALYSIS

Largest Discount Impact Orders

Find orders where discount percentage is highest.

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

Solve This SQL Challenge

The task

Find orders where discount percentage is highest.

A correct answer returns 200 rows with 11 columns: id, user_id, total, discount, item_count, status, order_date, shipped_date, shipping_city, shipping_country, discount_pct.

Tables used in this challenge

`orders` 200 rows

id INTEGER (PK) · user_id INTEGER · total REAL · discount REAL · item_count INTEGER · status TEXT · order_date TEXT · shipped_date TEXT · shipping_city TEXT · shipping_country TEXT

First 3 rows of the orders table
id	user_id	total	discount	item_count	status	order_date	shipped_date	shipping_city	shipping_country
1	43	2638.11	0.25	3	cancelled	2024-04-24	NULL	Los Angeles	USA
2	8	2947	0.19	5	delivered	2024-03-15	2023-04-09	Chicago	USA
3	136	683.24	0.08	2	delivered	2023-02-15	2023-07-10	Los Angeles	USA

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	user_id	total	discount	item_count	status	order_date	shipped_date	shipping_city	shipping_country	discount_pct
150	71	29.17	0.06	3	delivered	2022-02-11	2024-12-16	San Antonio	USA	0.2056907781967775
88	71	57.11	0.07	1	delivered	2023-11-19	2024-09-15	Chicago	USA	0.12257047802486432
155	69	110.6	0.11	6	cancelled	2024-12-19	NULL	San Jose	USA	0.09945750452079566
158	18	103.02	0.08	4	delivered	2023-03-01	2024-07-24	Austin	USA	0.07765482430596
106	28	77.71	0.06	5	delivered	2023-12-04	2024-03-02	Chicago	USA	0.07721014026508816

First 5 of 200 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

discount / total

Show the step-by-step approach

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

Read from the orders table.
Add the calculated column discount_pct: discount * 100.0 / total.
Sort the result by discount_pct descending.

Model solution

Checking your session…

What to watch for

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.