gistfile1.txt

CREATE OR REPLACE TRIGGER check_artist
  BEFORE INSERT ON genre_artist
  FOR EACH ROW
DECLARE
    artist_id INTEGER;
    new_id INTEGER;
BEGIN
    SELECT id INTO artist_id FROM jobs WHERE name = 'Artist';
    SELECT job INTO new_id FROM persons WHERE id = :new.artist;
    IF (artist_id != new_id) THEN
       RAISE_APPLICATION_ERROR(-20773, 'Not an artist!');
    END IF;
END;