oracle的case函数create sequence STUDENT_SEQUENCE;

CREATE TABLE students (
id NUMBER(5) PRIMARY KEY,
stu_name VARCHAR2(20),
score NUMBER(10,0),
grade varchar2(2));

INSERT INTO students (id, stu_name, score, grade)
VALUES (student_sequence.NEXTVAL, 'Scott', 98,null);

INSERT INTO students (id, stu_name, score, grade)
VALUES (student_sequence.NEXTVAL, 'Margaret', 88,null);

INSERT INTO students (id, stu_name, score, grade)
VALUES (student_sequence.NEXTVAL, 'Joanne', 75,null);

INSERT INTO students (id, stu_name, score, grade)
VALUES (student_sequence.NEXTVAL, 'Manish', 66,null);


update students
set grade =
case when score > 90 then 'a'
when score > 80 then 'b'
when score > 70 then 'c'
else 'd' end

oracle的case结构

begin
case when 2<1 then
dbms_output.put_line('y');
else
dbms_output.put_line('n');
end case;
end;
/

这个case when ... end case 和上边的case when ... end是不同的。