i want 2 create a trigger.Plz help as soon as possible

[prabhleen]

I have 2 tables namely COURSE and STUDENT with fields and constraints as follws

course

course_id number(4) PRIMARY KEY
course_name varchar2(50) NOT NULL
course_duration number(3)

student

roll_no number(4) PRIMARY KEY
name varchar2(50) NOT NULL
marks number(3)
grade char(1)
course_id number(4) FOREIGN KEY

Now i want to create a trigger on student table so that when i insert or update marks field the grade field should automatcally get updated or filled.

marks>80
grade =A
marks 80-70
grade = B
marks 70-60
grade =C
marks 60- 50
grade = D
marks 50-40
grade = E
marks<=40
grade = F

[sathishbk]

CREATE TABLE STUDENT
(
roll_no number(4) PRIMARY KEY,
name varchar2(50) NOT NULL,
marks number(3),
grade char(1),
course_id number(4)
)
/


CREATE TRIGGER TR_GRADE
BEFORE UPDATE OR INSERT ON STUDENT
FOR EACH ROW
BEGIN
IF :NEW.MARKS>80 THEN
:NEW.GRADE:='A';
ELSIF :NEW.MARKS>70 AND :NEW.MARKS<80 THEN
:NEW.GRADE:='B';
ELSIF :NEW.MARKS>60 AND :NEW.MARKS<70 THEN
:NEW.GRADE:='C';
ELSIF :NEW.MARKS>50 AND :NEW.MARKS<60 THEN
:NEW.GRADE:='D';
ELSIF :NEW.MARKS>40 AND :NEW.MARKS<50 THEN
:NEW.GRADE:='E';
ELSIF :NEW.MARKS<=40 THEN
:NEW.GRADE:='F';
END IF;
END TR_GRADE;
/

insert into student VALUES (1,'SATHISH',3,NULL,123);
SELECT * FROM STUDENT;
ROLL_NO NAME MARKS G COURSE_ID
---------- -------------------------------------------------- ---------- - ----------
1 SATHISH 3 F 123