ORACLE 行轉列的方法

前期準備

創建一個表

create table student_score(
    name varchar2(30),
    subject varchar(20),
    score number(4,1)
);

插入數據

insert into student_score (name,subject,score)values('張三','Chinese',90);
insert into student_score (name,subject,score)values('張三','Mathematics',80);
insert into student_score (name,subject,score)values('張三','English',79);

insert into student_score (name,subject,score)values('li shi','Chinese',96);
insert into student_score (name,subject,score)values('li shi','Mathematics',86);
insert into student_score (name,subject,score)values('li shi','English',76);

insert into student_score (name,subject,score)values('wang wu','Chinese',92);
insert into student_score (name,subject,score)values('wang wu','Mathematics',82);
insert into student_score (name,subject,score)values('wang wu','English',72);

以下命令

用decode命令

select name,
sum(decode(subject, 'Chinese', nvl(score, 0), 0)) "Chinese",
sum(decode(subject, 'Mathematics', nvl(score, 0), 0)) "Mathematics",
sum(decode(subject, 'English', nvl(score, 0), 0)) "English"
from student_score
group by name;

獲得結果：

NAME                              Chinese Mathematics    English
------------------------------ ---------- ----------- ----------
張三                                   90          80         79
wang wu                                92          82         72
li shi                                 96          86         76

用case then命令

SELECT NAME,
SUM(CASE WHEN SUBJECT='CHINESE'
THEN NVL(SCORE,0)
ELSE 0
END) "CHINESE",
SUM(CASE WHEN SUBJECT='MATHEMATICS'
THEN NVL(SCORE,0)
ELSE 0
END) "MATHEMATICS",
SUM(CASE WHEN SUBJECT='ENGLISH'
THEN NVL(SCORE,0)
ELSE 0
END) "ENGLISH"
FROM STUDENT_SCORE
GROUP BY NAME;

使用decode判斷字符串是否一樣

DECODE(value,if 條件1，then 值1，if 條件2，then 值2，...，else 其他值)