HardSQL challenge #260GROUP BYAGGREGATIONORDER BY

Top 5 Products by Revenue

Find top 5 products based on total revenue globally.

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

Solve This SQL Challenge

The task

Find top 5 products based on total revenue globally.

A correct answer returns 5 rows with 2 columns: product_id, revenue.

Tables used in this challenge

order_items 496 rows

id INTEGER (PK) · order_id INTEGER · product_id INTEGER · quantity INTEGER · unit_price REAL · subtotal REAL

First 3 rows of the order_items table
idorder_idproduct_idquantityunit_pricesubtotal
11765192.21961.05
21823107.1321.3
316515.395.39

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
product_idrevenue
1198995.83
388530.61
607519.96
327066.04
516944.33

The complete result: 5 rows. 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
  • Grouping rows with GROUP BY to get one result row per group
  • Sorting the result with ORDER BY
  • Returning only the first rows with LIMIT

Hint and approach

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

Show the hint

SUM + ORDER BY DESC LIMIT

Show the step-by-step approach

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

  1. Read from the order_items table.
  2. Group the rows by product_id, so the result has one row for each value.
  3. For each group, compute SUM(subtotal).
  4. Sort the result by revenue descending.
  5. Keep only the first 5 rows with LIMIT.

Model solution

Checking your session…

What to watch for

  • GROUP BY. Every selected column must either be in GROUP BY or sit inside an aggregate. SQLite accepts other columns and returns an arbitrary value for them; most databases raise an error.
  • LIMIT. LIMIT without ORDER BY returns an arbitrary set of rows. LIMIT is also dialect-specific: SQL Server uses TOP and Oracle uses FETCH FIRST.
  • 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.
Solve This SQL Challenge

Keep learning