Health Data Clinic - Book 11: Aggregating & Reporting Data

Ten thousand rows answer nothing on their own. What a manager wants is one number, and this book is about producing it. You work through the five aggregate functions, COUNT, SUM, AVG, MIN and MAX, with a careful chapter on the difference between COUNT(*) and COUNT of a named column, which is where empty values quietly change your answer. You combine aggregates with WHERE to summarize a filtered set, then move to GROUP BY and summarize per group, counting rows per group and totaling values per group. A billing report puts both to work on real clinic data. HAVING follows, along with a direct comparison of WHERE and HAVING that settles which one filters what and when each runs. The final chapter builds reports across joined tables, so your summaries can draw on more than one table at a time, which is where a plain row count turns into a report someone will actually use.

Twenty-five A4 pages, in full color. Written in short sentences and plain English, for readers whose first language is not English and clearer for everyone else because of it.

Every query in this book was run against a live database before the page was printed, so the result you read is the result you get. Instant PDF download. By M.R. Sterling.