Chapter One · The Problem
Why Databases Exist
Before a single table or query, this chapter earns the whole subject: the specific, predictable ways that files and spreadsheets fail once data is shared — told through one small cinema's very bad Saturday. Then the fix gets a proper name (two names, actually — the database and the DBMS guarding it), the cinema we'll follow all book gets a proper introduction, and the map of database families goes on the wall so you always know where you are.
Nobody falls in love with databases through definitions. You fall in love — or at least into respect — the first time you watch shared data go wrong: the booking that vanished because two people saved at once, the two copies of the schedule that quietly disagree, the typo that became a stored fact. This chapter starts there, with the failures, because every database idea in the rest of the book is an answer to one of them.
Four topics build the foundation. First, the failures themselves — what actually breaks when a spreadsheet becomes shared, and why care alone can't fix it. Then the fix, properly defined: the database, the DBMS standing guard in front of it, and your first friendly look at SQL. Then a real introduction to the Marquee — the two-screen cinema whose films, screenings, customers, and bookings carry every example in this book. And finally the honest map: the relational family this course teaches, the NoSQL families around it, and the rule of thumb for telling them apart.