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Revenue by Product Category

Finance wants a quick view of which product categories bring in the most money. Calculate total revenue per category, counting only completed orders. Line revenue is quantity times unit_price.

Expected output: category, revenue (rounded to 2 decimals). Highest revenue first.

customers(customer_id, name, country, signup_date, referred_by)

products(product_id, name, category, price)

orders(order_id, customer_id, order_date, status)

order_items(order_id, product_id, quantity, unit_price)

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Expected output preview (5 rows, order matters)
categoryrevenue
Electronics8311.74
Home6169.04
Apparel4783.72

Showing 3 of 5 rows.

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70 original problems on window functions, retention cohorts, funnels, self-joins and attribution. 24 easy · 30 medium · 16 hard · 12 free without an account

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Four realistic datasets

E-commerce store

An online store selling electronics, home goods, books, apparel and beauty products to customers in six countries (Jan 2025 to Mar 2026).

customers · products · orders · order_items

Ride-share marketplace

Trip requests in four US cities from January to March 2026, with drivers, riders, fares and ratings.

drivers · riders · trips

B2B SaaS product events

A project-management SaaS: company accounts, their users, product event logs (Jan to Apr 2026) and subscription history.

accounts · users · events · subscriptions

Digital ads performance

A retailer's paid campaigns across search, social, display and video in February 2026: daily delivery, individual ad clicks and purchases.

campaigns · ad_daily · ad_clicks · conversions

Practise by topic

Aggregation & GROUP BYCOUNT, SUM, AVG, GROUP BY and HAVING.JoinsInner, left and anti-joins, plus fan-out traps.Conditional AggregationCASE inside SUM/AVG to pivot metrics.Window FunctionsOVER, PARTITION BY, LAG/LEAD and frames.Ranking & Top-N per GroupROW_NUMBER, RANK and DENSE_RANK.Running Totals & Rolling WindowsCumulative sums, moving averages, Pareto cuts.Retention & CohortsCohort tables, new vs returning users.Funnels & ActivationOrdered funnels and time-boxed conversion.Self-JoinsJoining a table to itself: referrals, pairs, transitions.Dates & TimeTruncation, date math and calendar buckets.Subqueries & CTEsStep-by-step queries with WITH.Marketing AttributionFirst-touch, last-touch, linear and ROAS.Gaps & IslandsStreaks and sessionization.

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