HardSQL challenge #285WINDOW FUNCTIONPARTITIONPERCENTILE

Daily Revenue Percentile

Find percentile of each order within its day.

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 percentile of each order within its day.

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, 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
58	137	1843.49	0.19	3	pending	2022-01-06	NULL	Los Angeles	USA
4	115	3920.44	0.08	4	processing	2022-01-10	NULL	San Jose	USA
89	15	1152.13	0.09	3	pending	2022-01-15	NULL	Fort Worth	USA
101	55	3391.66	0.1	5	delivered	2022-01-16	2024-02-26	Austin	USA
8	91	4163.77	0.2	2	delivered	2022-01-17	2023-08-22	Indianapolis	USA

First 5 of 200 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

Expressing a row's position as a fraction with PERCENT_RANK()
Restarting a window calculation for each group with PARTITION BY

Hint and approach

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

Show the hint

PERCENT_RANK partition

Show the step-by-step approach

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

Read from the orders table.
Compute PERCENT_RANK(), the relative position from 0 to 1, ordered by total, restarting for each order_date.

Model solution

Checking your session…

What to watch for

PERCENT_RANK(). PERCENT_RANK() returns a value between 0 and 1, not a percentage. Multiply by 100 to display it as one.
PARTITION BY. PARTITION BY is not GROUP BY: it keeps every row and only decides which rows a window function looks at.