CREATE TABLE public.course_professor_levels
(
    id integer NOT NULL DEFAULT nextval('course_professor_levels_id_seq'::regclass),
    course_id integer NOT NULL,
    professor_id bigint NOT NULL,
    level_id integer,
    CONSTRAINT course_professor_levels_course_id_fkey FOREIGN KEY (course_id) REFERENCES courses(course_id) ON DELETE CASCADE,
    CONSTRAINT course_professor_levels_level_id_fkey FOREIGN KEY (level_id) REFERENCES levels(level_id) ON DELETE SET NULL,
    CONSTRAINT course_professor_levels_professor_id_fkey FOREIGN KEY (professor_id) REFERENCES partners(partner_id) ON DELETE CASCADE,
    CONSTRAINT course_professor_levels_pkey PRIMARY KEY (id),
    CONSTRAINT course_professor_levels_course_id_professor_id_level_id_key UNIQUE (course_id, professor_id, level_id)
);