快捷導(dǎo)航

Oracle case函數(shù)使用介紹

更新時(shí)間：2013年09月25日 12:28:32 作者：

這篇文章主要通過實(shí)例簡(jiǎn)要介紹case函數(shù)的用法，學(xué)習(xí)oracle的朋友可以參考下

1.創(chuàng)建測(cè)試表:

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;

2.查看相應(yīng)數(shù)據(jù)

復(fù)制代碼代碼如下:

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.更新語句

復(fù)制代碼代碼如下:

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.更新后結(jié)果

復(fù)制代碼代碼如下:

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

您可能感興趣的文章: