The journey of every round

I bought a sofa that's a different colour than what I saw on the website. What are my rights?

I bought online but didn't open the box for 30 days. Can I still return it?

The retailer is offering a credit note instead of a refund. Can I insist on cash?

I bought a kettle that broke after 3 weeks. Am I entitled to a refund under UK consumer law?

Find the date with the highest number of new signups in a users table.

Use HAVING to filter aggregate results: orders with more than 5 line items.

Write a SQL query joining 4 tables (customers, orders, line_items, products) to produce a customer-order-product report.

Find products in the top 10 percent by revenue using NTILE.

Calculate the gap in days between consecutive logins per user using LAG.

Use EXISTS to find customers with at least one cancelled order.

Find the median salary in each department using window functions.

Write a recursive CTE to walk an employee-manager hierarchy from any starting employee.

Use UNION to combine current_employees and former_employees, marking source.

Find orders where the order_date is later than the ship_date.

Write a SQL query that returns products and their cumulative sales over time.

Calculate a moving 7-day average of daily_sales using a window function.

Find customers who placed orders in consecutive calendar months.

Pivot a table of monthly_sales (month, year, total) to columns per month.

Use ROW_NUMBER to deduplicate orders, keeping the most recent per customer.

Find duplicate rows in an emails table based on email address.

Write a self-join to find pairs of employees with the same manager.

Calculate the percentage of total sales each product represents.

Use a CTE to find the longest chain of referrals in a referrals table.

Write a SQL query that returns customers with more than 3 orders.