1.创建测试表:
代码如下: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,'Margaret','Mason','History',88,'Joanne','Junebug',75,'Manish','Murgratroid','Economics',66,null);
commit;
2.查看相应数据
代码如下: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
3.更新语句
代码如下: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
)
/
4.更新后结果
代码如下: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
（编辑：李大同）
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