Триггер на подсчет студентов для таблицы факультет из таблицы студент

CREATE TABLE  "STUDENT" 
   (    "N_STUDENT" NUMBER NOT NULL ENABLE, 
    "N_FACULTY" NUMBER, 
    "MODEOFSTUDY" VARCHAR2(20) NOT NULL ENABLE, 
    "C_LAST_NAME" VARCHAR2(20) NOT NULL ENABLE, 
    "C_FIRST_NAME" VARCHAR2(20) NOT NULL ENABLE, 
    "C_SECOND_NAME" VARCHAR2(20), 
    "SPECIALTY" VARCHAR2(20) NOT NULL ENABLE, 
    "COURSE" NUMBER, 
    "N_GROUP" NUMBER, 
     CONSTRAINT "STUDENT_PK" PRIMARY KEY ("N_STUDENT") ENABLE
   ) ;ALTER TABLE  "STUDENT" ADD CONSTRAINT "STUDENT_FK1" FOREIGN KEY ("N_FACULTY")
      REFERENCES  "FACULTY" ("N_FACULTY") ON DELETE SET NULL ENABLE;

CREATE TABLE  "FACULTY" 
   (    "N_FACULTY" NUMBER NOT NULL ENABLE, 
    "C_FACULTY" VARCHAR2(20) NOT NULL ENABLE, 
    "COUNT_STUDENT" NUMBER, 
     CONSTRAINT "FACULTY_PK" PRIMARY KEY ("N_FACULTY") ENABLE
   ) ;

CREATE OR REPLACE TRIGGER COUNT_SF
AFTER INSERT OR UPDATE OR DELETE OF COUNT_STUDENT ON FACULTY
BEGIN
DECLARE STUDENT NUMBER(10);
DECLARE N_COUNT_STUDENT NUMBER(10);
  IF deleting THEN
    STUDENT = OLD.N_STUDENT;
  ELSE
    STUDENT = NEW.N_STUDENT;
 
  SELECT COUNT(N_STUDENT) 
    FROM STUDENT
   WHERE N_STUDENT=:STUDENT
   GROUP BY N_FACULTY
    INTO :N_COUNT_STUDENT;
 
  UPDATE FACULTY
     SET COUNT_STUDENT = :N_COUNT_STUDENT
   WHERE STUDENT = :STUDENT;
END;