Oracle行列轉換小結

目錄結構如下：

• 行轉列
• 列轉行

[一]、行轉列

 

1.1、初始測試數據

 

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
)

 初始數據如下圖：

                        

 

1.2、 如果需要實現如下的查詢效果圖：

                     

 

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分組實現的，具體的sql如下：

select t.user_name,
  sum(decode(t.course, '語文', 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

 

 

1.3、延伸

 

如果要實現對各門功課的不同分數段進行統計，效果圖如下：

                 

 

具體的實現sql如下：

select t2.SCORE_GP,
  sum(decode(t2.course, '語文', 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 >=60 and t.score <80  then '60-80'
              when t.score >=80 then '80-100' end
  order by t.course ) t2
group by t2.SCORE_GP
order by t2.SCORE_GP

 

[二]、列轉行

 

1.1、初始測試數據

        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
)

 

        初始數據如下圖：

        

 

1.2、 如果需要實現如下的查詢效果圖：

                       

 

這就是最常見的列轉行，主要原理是利用SQL裏面的union，具體的sql語句如下：

select user_name, '語文' 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

 

 也可以利用【 insert all into ... select 】來實現，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
    )

 再執行下面的sql：

 

insert all
into test_tb_grade3(USER_NAME,COURSE,SCORE) values(user_name, '語文', 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;

 別忘記commit操作，然後再查詢TEST_TB_GRADE3，發現表中的數據就是列轉成行了。

 

 

本文連接：http://sjsky.iteye.com/blog/1152167

 

 

轉載請註明來自：Michael's blog @ http://sjsky.iteye.com