SQL Training

Understand the idea

Create four outputs: available products, paid sales by customer, daily paid revenue, and order-total mismatches. Record the grain and units of every output. Add a customer with no orders and two orders on one date to test edge cases. The worked query below is the daily revenue report; keep its paid-status rule explicit in your project notes.

Where to try it

Run this example in the SQL playground. The lesson link loads the shop tables and sample rows before this query. Select Run when you are ready. Every run starts fresh, so your changes do not affect the website or a previous run.

SQLite sample data · MySQL / MariaDB sample data · See the sample tables

Your task

Complete the four reports, document one edge case for each, and review a query plan after adding realistic amounts of test data.

SELECT ordered_at AS sales_date, COUNT(*) AS paid_orders,
       SUM(total_cents) AS paid_cents
FROM orders WHERE status = 'paid'
GROUP BY ordered_at
ORDER BY ordered_at;