CREATE TRIGGER tr_check_req
AFTER INSERT ON HW3.SCHEDULE
REFERENCING NEW AS nROW
FOR EACH ROW MODE DB2SQL
BEGIN
DECLARE preReqFound BOOLEAN DEFAULT FALSE;
FOR v1 AS
      c1 CURSOR FOR
   SELECT * FROM HW3.CLASSREQ WHERE ClassId = nROW.ClassId
   DO
      IF( EXISTS(
        SELECT 1 FROM HW3.SCHEDULE WHERE StudentId = nROW.StudentId AND ClassId = PrereqId AND
        ( YEAR != nRow.YEAR AND Semester != nRow.Semester) AND Coreq = 'F')
        )
      THEN SET preReqFound = TRUE ;
      END IF;

      IF( EXISTS(
        SELECT 1 FROM HW3.SCHEDULE WHERE StudentId = nROW.StudentId AND ClassId = PrereqId AND Coreq = 'T')
        )
      THEN SET preReqFound = TRUE ;
      END IF;
  END FOR;
  IF preReqFound = FALSE
  THEN SIGNAL SQLSTATE '88888' ('Student does not have prerequisite OR co-requisite');

END