Trigger

CREATE TRIGGER validate BEFORE INSERT ON actividades.ce_relalummat
FOR EACH ROW
	BEGIN
		DECLARE record CURSOR FOR SELECT cve_externa FROM actividades.ce_materias  WHERE cve_materia=NEW.cve_materia;
		OPEN record;
		FETCH record INTO number;
		IF number<0 THEN
			INSERT INTO ce_relalummat VALUES(NULL,NEW.cve_alumno,NEW.cve_materia,51,1);
		END IF
		CLOSE numero;
	END