modify sql code

[gamer2d]

How can I change the below oracle sql code so that: The current enrollment of an offering must be less than the maximum enrollment.

CREATE TABLE COURSES
  (COURSE VARCHAR(6),
   DESCRIPTION VARCHAR(60),
   CREDITS INT,
   CONSTRAINT pk PRIMARY KEY (COURSE));

CREATE TABLE OFFERINGS
( CRN INT,
  COURSE VARCHAR(6),
  SECTION VARCHAR(2),
  DATES VARCHAR(5),
  TIMES VARCHAR(30),
  INSTRUCTOR VARCHAR(30),
  ROOM VARCHAR(20),
  ENROLLMAX INT,
  ENROLLCURRENT INT,
  CONSTRAINT pk2 PRIMARY KEY (CRN),
  CONSTRAINT fk1 FOREIGN KEY (COURSE) REFERENCES COURSES (COURSE));

CREATE TABLE STUDENTS
( USERID VARCHAR(9),
  PASSWORD VARCHAR(10),
  FIRSTNAME VARCHAR(20),
  LASTNAME VARCHAR(30),
  PHONE VARCHAR(12),
  DOB VARCHAR(40),
  MAJOR VARCHAR(20),
  ADDRESS VARCHAR(30),
  CITY VARCHAR(30),
  STATE VARCHAR(2),
  ZIP VARCHAR(5),
  CONSTRAINT pk3 PRIMARY KEY (USERID));

CREATE TABLE ENROLLMENTS
( CRN INT,
  USERID VARCHAR(9),
  ENROLLDATE VARCHAR(30),
  GRADE VARCHAR(2),
  CONSTRAINT pk4 PRIMARY KEY(CRN, USERID),
  CONSTRAINT fk2 FOREIGN KEY (CRN) REFERENCES OFFERINGS(CRN),
  CONSTRAINT fk3 FOREIGN KEY (USERID) REFERENCES STUDENTS(USERID));