EasySQL challenge #30SUM

Total Discounts

Find total discount given on orders.

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 total discount given on orders.

A correct answer returns 1 row with one column: SUM(discount).

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
SUM(discount)
24.94

The complete result: 1 row. This is the output of the model solution on the practice database.

What you practise

Summarising many rows into one value with COUNT, SUM, AVG, MIN or MAX

Hint and approach

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

Show the hint

Use SUM

Show the step-by-step approach

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

Read from the orders table.
Aggregate over all the rows that are left: compute SUM(discount). With no GROUP BY, the result is a single row.

Model solution

Checking your session…

What to watch for

Aggregate functions. Aggregates skip NULLs. AVG divides by the number of non-NULL values and COUNT(column) can be smaller than COUNT(*).