Part of the "SQL: Zero to Ninja" series, written for junior web devs. Picture this. A user pays for an order. Your code creates the order row. Then, right before it saves the items... the server crashes. Now you have a paid order with nothing in it. The customer is angry, your data is broken, and you are debugging at 2am. A transaction is the seatbelt that stops this. Let's learn it. The idea in one line A transaction groups several statements into one all-or-nothing unit: either they all succeed, or none of them happen. The metaphor: carrying a couch with a friend You and a friend are carrying a heavy couch up the stairs. The rule is simple: you both lift, or you both stop. You never leave the couch half-lifted, balanced on the stairs, while one of you wanders off. That is dangerous and silly. A transaction is the same deal between your statements. They go up the stairs together, or they do not go at all. Half-done is NOT allowed: [ subtract money from A ] done [ add money to B ] crash!…