Write a portfolio query on a mini e-commerce dataset

Why it matters

Data recruiters skip long explanations. They read your query for 30 seconds and know your level.

Steps

• Create customers (id, name, city, signup_date) and orders (id, customer_id, amount, order_date) with 20 rows each
• Query 1: revenue per city this month (JOIN plus GROUP BY plus SUM)
• Query 2: top 5 customers plus average order (ORDER BY plus LIMIT plus AVG)
• Query 3: customers with no orders in 60 days (LEFT JOIN plus WHERE NULL)
• Comment each block: what is computed and why

Expected output

.sql file with 3 commented queries plus results plus 3 insight lines

Checklist

• Queries run error-free
• Comments explain why, not what
• NULLs handled
• Insights cite specific numbers

Evidence

SQL file plus result screenshots

Self review

Could a junior follow your logic from comments alone?