DROP SEQUENCE student_sequence;

            CREATE SEQUENCE student_sequence  START WITH 10000  INCREMENT BY 1;

            

            DROP TABLE students;

            CREATE TABLE students (

            id               NUMBER(5) PRIMARY KEY,

            first_name       VARCHAR2(20),

            last_name        VARCHAR2(20),

            major            VARCHAR2(30),

            current_credits  NUMBER(3),

            grade     varchar2(2));

            

            INSERT INTO students (id, first_name, last_name, major, current_credits,grade)

            VALUES (student_sequence.NEXTVAL, 'Scott', 'Smith', 'Computer Science', 98,null);

            

            INSERT INTO students (id, first_name, last_name, major, current_credits,grade)

            VALUES (student_sequence.NEXTVAL, 'Margaret', 'Mason', 'History', 88,null);

            

            INSERT INTO students (id, first_name, last_name, major, current_credits,grade)

            VALUES (student_sequence.NEXTVAL, 'Joanne', 'Junebug', 'Computer Science', 75,null);

            

            INSERT INTO students (id, first_name, last_name, major, current_credits,grade)

            VALUES (student_sequence.NEXTVAL, 'Manish', 'Murgratroid', 'Economics', 66,null);

            

            commit;

            

SQL> select * from students;

            

            ID FIRST_NAME           LAST_NAME            MAJOR                          CURRENT_CREDITS GR

            ---------- -------------------- -------------------- ------------------------------ --------------- --

            10000 Scott                Smith                Computer Science                            98

            10001 Margaret             Mason                History                                     88

            10002 Joanne               Junebug              Computer Science                            75

            10003 Manish               Murgratroid          Economics                                   66

            

update students

            set grade = (

            select grade from

            (

            select id,

            case when current_credits > 90 then 'a'

            when current_credits > 80 then 'b'

            when current_credits > 70 then 'c'

            else 'd' end grade

            from students

            ) a

            where a.id = students.id

            )

            /

            

SQL> select * from students;

            

            ID FIRST_NAME           LAST_NAME            MAJOR                          CURRENT_CREDITS GR

            ---------- -------------------- -------------------- ------------------------------ --------------- --

            10000 Scott                Smith                Computer Science                            98 a

            10001 Margaret             Mason                History                                     88 b

            10002 Joanne               Junebug              Computer Science                            75 c

            10003 Manish               Murgratroid          Economics                                   66 d