SQLite multi-Primary Key on a Table, one of them is Auto Increment

Question

I have multiple (composite) primary keys on a table and one of them will be auto increment. However, interestingly SQLite allows usage of AUTOINCREMENT keyword

Answer 1

UNIQUE INDEX alone doesn't have the same effect as PRIMARY KEY. A unique index will allow a NULL; a primary key constraint won't. You're better off declaring both those constraints.

CREATE TABLE ticket (
     id INTEGER PRIMARY KEY AUTOINCREMENT,
     seat TEXT NOT NULL, 
     payment INTEGER,
     UNIQUE (id, seat));

You should also think hard about whether you really need to accept NULL payments.