目錄結構如下：
行轉列
列轉行
[一]、行轉列
1.1、初始測試資料
表結構：TEST_TB_GRADE
create table TEST_TB_GRADE
(
ID NUMBER(10) not null,
USER_NAME VARCHAR2(20 CHAR),
COURSE VARCHAR2(20 CHAR),
SCORE FLOAT
)
<b>[sql]</b>
create table TEST_TB_GRADE
(
ID NUMBER(10) not null,
USER_NAME VARCHAR2(20 CHAR),
COURSE VARCHAR2(20 CHAR),
初始資料如下圖：
1.2、
如果需要實作如下的查詢效果圖：
這就是最常見的行轉列，主要原理是利用decode函數、聚集函數(sum)，結合group
by分組實作的，具體的sql如下：
select t.user_name,
sum(decode(t.course, ‘國文‘, score,null)) as CHINESE,
sum(decode(t.course, ‘數學‘, score,null)) as MATH,
sum(decode(t.course, ‘英語‘, score,null)) as ENGLISH
from test_tb_grade t
group by t.user_name
order by t.user_name
select t.user_name,
sum(decode(t.course, ‘國文‘, score,null)) as CHINESE,
sum(decode(t.course, ‘數學‘, score,null)) as MATH,
sum(decode(t.course, ‘英語‘, score,null)) as ENGLISH
from test_tb_grade t
group by t.user_name
1.3、延伸
如果要實作對各門功課的不同分數段進行統計，效果圖如下：
具體的實作sql如下：
select t2.SCORE_GP,
sum(decode(t2.course, ‘國文‘, COUNTNUM,null)) as CHINESE,
sum(decode(t2.course, ‘數學‘, COUNTNUM,null)) as MATH,
sum(decode(t2.course, ‘英語‘, COUNTNUM,null)) as ENGLISH
from (
select t.course,
case when t.score <60 then ‘00-60‘
when t.score >=60 and t.score <80 then ‘60-80‘
when t.score >=80 then ‘80-100‘ end as SCORE_GP,
count(t.score) as COUNTNUM
FROM test_tb_grade t
group by t.course,
case when t.score <60 then ‘00-60‘
when t.score >=80 then ‘80-100‘ end
order by t.course ) t2
group by t2.SCORE_GP
order by t2.SCORE_GP
select t2.SCORE_GP,
sum(decode(t2.course, ‘國文‘, COUNTNUM,null)) as CHINESE,
sum(decode(t2.course, ‘數學‘, COUNTNUM,null)) as MATH,
sum(decode(t2.course, ‘英語‘, COUNTNUM,null)) as ENGLISH
from (
select t.course,
when t.score >=80 then ‘80-100‘ end as SCORE_GP,
count(t.score) as COUNTNUM
FROM test_tb_grade t
group by t.course,
order by t.course ) t2
group by t2.SCORE_GP
[二]、列轉行
表結構：TEST_TB_GRADE2
create table TEST_TB_GRADE2
ID NUMBER(10) not null,
USER_NAME VARCHAR2(20 CHAR),
CN_SCORE FLOAT,
MATH_SCORE FLOAT,
EN_SCORE FLOAT
create table TEST_TB_GRADE2
ID NUMBER(10) not null,
USER_NAME VARCHAR2(20 CHAR),
CN_SCORE FLOAT,
MATH_SCORE FLOAT,
初始資料如下圖：
這就是最常見的列轉行，主要原理是利用SQL裡面的union，具體的sql語句如下：
select user_name, ‘國文‘ COURSE , CN_SCORE as SCORE from test_tb_grade2
union select user_name, ‘數學‘ COURSE, MATH_SCORE as SCORE from test_tb_grade2
union select user_name, ‘英語‘ COURSE, EN_SCORE as SCORE from test_tb_grade2
order by user_name,COURSE
select user_name, ‘國文‘ COURSE , CN_SCORE as SCORE from test_tb_grade2
union select user_name, ‘數學‘ COURSE, MATH_SCORE as SCORE from test_tb_grade2
union select user_name, ‘英語‘ COURSE, EN_SCORE as SCORE from test_tb_grade2
也可以利用【 insert all into ...
select 】來實作，首先需要先建一個表TEST_TB_GRADE3：
create table TEST_TB_GRADE3
(
USER_NAME VARCHAR2(20 CHAR),
COURSE VARCHAR2(20 CHAR),
SCORE FLOAT
)
create table TEST_TB_GRADE3
(
USER_NAME VARCHAR2(20 CHAR),
COURSE VARCHAR2(20 CHAR),
SCORE FLOAT
再執行下面的sql：
insert all
into test_tb_grade3(USER_NAME,COURSE,SCORE) values(user_name, ‘國文‘, CN_SCORE)
into test_tb_grade3(USER_NAME,COURSE,SCORE) values(user_name, ‘數學‘, MATH_SCORE)
into test_tb_grade3(USER_NAME,COURSE,SCORE) values(user_name, ‘英語‘, EN_SCORE)
select user_name, CN_SCORE, MATH_SCORE, EN_SCORE from test_tb_grade2;
commit;
into test_tb_grade3(USER_NAME,COURSE,SCORE) values(user_name, ‘國文‘, CN_SCORE)
into test_tb_grade3(USER_NAME,COURSE,SCORE) values(user_name, ‘數學‘, MATH_SCORE)
into test_tb_grade3(USER_NAME,COURSE,SCORE) values(user_name, ‘英語‘, EN_SCORE)
select user_name, CN_SCORE, MATH_SCORE, EN_SCORE from test_tb_grade2;
别忘記commit操作，然後再查詢TEST_TB_GRADE3，發現表中的資料就是列轉成行了。
本文連接配接：http://sjsky.iteye.com/blog/1152167
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