SQL Reports YOU CAN TRUST: Build, Check, and Explain Business After Excel

Your SQL can run without errors-and still give you the wrong number. SQL Reports You Can Trust is a hands-on reporting book for people who are comfortable with Excel but are beginning to work with relational databases. Using a small fictional retail business and PostgreSQL, it shows how to turn orders, payments, refunds, dates, and customer data into reports you can actually explain and verify. Learn to catch the mistakes that look correct. You'll see how duplicated joins inflate sales, missing rows disappear silently, NULL values distort totals, date boundaries move transactions into the wrong month, and the wrong denominator can produce a believable but false average. Twenty controlled defect cases let you inspect the bad result, find the cause, and compare it with a corrected calculation. Build reports with evidence behind them. The book covers report grain, source checks, safe joins, aggregation, payment and refund reconciliation, time zones and cutoffs, window functions, independent controls, and repeatable refresh procedures. Each concept is tied to a real reporting question instead of being taught as isolated SQL syntax. What will you be able to do? Write SQL reports with clear business definitions, trace totals back to source records, recognize double counting and missing data, reconcile sales with payments and refunds, validate results before release, and hand another analyst a report they can reproduce and understand. From spreadsheets to trustworthy reporting. If you are moving from Excel into SQL and want more than queries that simply "run," this book gives you a practical method for producing business reports whose numbers you can check, explain, and trust.