Part of the "SQL: Zero to Ninja" series, for junior web devs who want SQL to finally click. Up to now, the tables already existed. You just queried them. But who decided that price holds numbers and email holds text? Who made sure two users can never share the same email? That was the person who designed the table . Today that person is you. The idea in one line CREATE TABLE builds a table, data types say what kind of thing each column holds, and constraints are rules the database promises to enforce so bad data can never sneak in. The metaphor: a table is a sign-up form Think of a table definition like a good sign-up form on a website. Each field has the right input type . The birthday field is a date picker, not a free text box where someone types "next Tuesday". Some fields are required . You cannot submit without an email. Some fields must be unique . You cannot sign up with an email someone already used. Some fields have a default . If you leave "newsletter" alone, it is set for you.…