Trigger of 'effin doom

gistfile1.sql

DROP TRIGGER CourseOverFlowTrigger;
CREATE TRIGGER CourseOverflowTrigger
    INSTEAD OF INSERT ON WaitingListView 
        REFERENCING NEW AS NewRow
                    OLD AS OldRow
        FOR EACH ROW
        DECLARE maxStudents         NUMBER;
                regedStudents       NUMBER;
                maxPlacement        NUMBER;
                numMissingCourses   NUMBER;
                listPlacements      NUMBER;
        BEGIN
            SELECT nrStudents INTO maxStudents FROM LimitedCourses WHERE LimitedCourses.code = :NewRow.course;
            SELECT COUNT(status) INTO regedStudents FROM WaitingListView WHERE status = 'REGISTERED' AND Course = :NewRow.course;
            SELECT nvl(MAX(placement),0) INTO maxPlacement FROM QueueingFor WHERE course = :NewRow.course;

            -- Have we missed some pre-req?
            SELECT COUNT(*) INTO numMissingCourses FROM
                ((SELECT RequiredCourse as c FROM Requires WHERE Requires.course = :NewRow.course)
                MINUS
                (SELECT COURSE as c FROM Completed WHERE Completed.Student = :NewRow.student));

            -- Are we on either the waiting list or registeredFor list already?
            SELECT COUNT(*) INTO listPlacements FROM
                 ((SELECT Student FROM RegisteredFor WHERE RegisteredFor.Student = :NewRow.student)
                UNION
                (SELECT Student FROM QueueingFor WHERE QueueingFor.Student = :NewRow.student));

            IF (regedStudents > maxStudents) THEN -- There are too many students
                IF (listPlacements = 0) THEN      -- Have we previously enqueued ourselves?
                    INSERT INTO test VALUES ('Student has no prior list placement (ALL OK!)');
                    INSERT INTO test VALUES ('RegedStudents > maxStudents, Enqueueing student.');
                    INSERT INTO QueueingFor VALUES (:NewRow.course, :NewRow.student, maxPlacement+1); 
                END IF;
            ELSE -- There is room for us!
                INSERT INTO test VALUES ('RegedStudents < maxStudents, Checking validity...');
                IF (numMissingCourses = 0) THEN -- Have we taken all the pre-reqs?
                    INSERT INTO test VALUES ('Student has taken pre-reqs');
                    IF (listPlacements = 0) THEN -- Are we already enrolled, or enqueued?
                        INSERT INTO test VALUES ('Student has no prior list placement (ALL OK!)');
                        INSERT INTO RegisteredFor VALUES (:NewRow.course, :NewRow.student);
                    END IF;
                ELSE
                    INSERT INTO test VALUES ('Student has NOT taken pre-reqs');
                END IF;
            END IF;
        END; 
.
run;