DECLARE
   v_count   NUMBER;
   a         NUMBER;
BEGIN
   SELECT COUNT (*)
     INTO v_count
     FROM login
    WHERE username = :login.username AND passwrd = :login.passwrd;

   IF v_count = 1
   THEN
      :GLOBAL.abc := :login.username;
      CALL_FORM ('enrollment');
   ELSE
      a := SHOW_ALERT ('ALERT_INVALID');
   END IF;
EXCEPTION
   WHEN OTHERS
   THEN
      a := SHOW_ALERT ('ALERT_LOGIN_ERROR');
END;

DECLARE
    v_status char(1) := 'N';
    v_courseid number;
    a number;
      
 BEGIN
      
   IF :exam_date IS NULL
   THEN
      MESSAGE ('enter the Exam date');
  
   ELSIF :course IS NULL
   THEN
      MESSAGE ('select the coursename');
   ELSIF :exam_paper IS NULL
   THEN
      MESSAGE ('select the exam paper');
   END IF;
 
 
   SELECT course_id
     INTO v_courseid
     FROM online_course
     WHERE course = :block3.course
     AND exam_paper = :block3.exam_paper;

if :exam_date > sysdate then
   INSERT INTO onlin_enroll(exam_id, user_name, course_id, exam_date,enrollment_date, status)
   VALUES(exa_id_seq.nextval, :global.abc, v_courseid, :exam_date,sysdate, v_status);
   message(:global.abc);
   COMMIT;
else
 a:= show_alert('alert_exam');
 end if;  
   exception
    when others then
  
   a:=show_alert('alert_error'); 
END;