> is better formulated as "PruefungsID integer primary key" which makes it an alias for the rowid, which is guaranteed to be NOT NULL and greater than zero. Not fully true with respect to "... greater than zero": ``` CREATE TABLE t(a INTEGER PRIMARY KEY, b TEXT); INSERT INTO t(a,b) VALUES (-1,'Minus One'),(0,'Zero'), (1,'One'),(2,'Two'); SELECT * FROM t; -- a |b -- ----|----------- -- -1 |Minus One -- 0 |Zero -- 1 |One -- 2 |Two DROP TABLE t; ``` I think the only restriction is that it HAS to be an Integer that fits inside a 64-bit signed value range/space.