oracle 行转列,列转行

[一]、行转列

1.1、初始测试数据

表结构：TEST_TB_GRADE

create table TEST_TB_GRADE   
(   
  ID        NUMBER(10) not null,   

  USER_NAME VARCHAR2(20 CHAR),   

  COURSE    VARCHAR2(20 CHAR),   

  SCORE     FLOAT  

)

初始数据如下图：

1.2、如果需要实现如下的查询效果图：

这就是最常见的行转列，主要原理是利用decode函数、聚集函数(sum)，结合group by分组实现的，具体的sql如下：

select t.user_name,   
sum(decode(t.course, '语文', score,null)) as CHINESE,   
sum(decode(t.course, '数学', score,null)) as MATH,   
sum(decode(t.course, '英语', score,null)) as ENGLISH   
from test_tb_grade t   
group by t.user_name   
order by t.user_name

1.3、延伸

如果要实现对各门功课的不同分数段进行统计，效果图如下：

select t2.SCORE_GP,
  sum(decode(t2.course, '语文', COUNTNUM,null)) as CHINESE,
  sum(decode(t2.course, '数学', COUNTNUM,null)) as MATH,
  sum(decode(t2.course, '英语', 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]、列转行

1.1、初始测试数据

表结构：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  
)

初始数据如下图：

1.2、如果需要实现如下的查询效果图：

这就是最常见的列转行，主要原理是利用SQL里面的union，具体的sql语句如下：

select user_name, '语文' COURSE , CN_SCORE as SCORE from test_tb_grade2    
union select user_name, '数学' COURSE, MATH_SCORE as SCORE from test_tb_grade2    
union select user_name, '英语' COURSE, EN_SCORE as SCORE from test_tb_grade2    
order by user_name,COURSE

也可以利用【 insert all into ... select 】来实现，首先需要先建一个表TEST_TB_GRADE3：

create table TEST_TB_GRADE3     
    (    
      USER_NAME VARCHAR2(20 CHAR),     
      COURSE    VARCHAR2(20 CHAR),     
      SCORE     FLOAT     
    )

再执行下面的sql：

insert all  
into test_tb_grade3(USER_NAME,COURSE,SCORE) values(user_name, '语文', CN_SCORE)   
into test_tb_grade3(USER_NAME,COURSE,SCORE) values(user_name, '数学', MATH_SCORE)   
into test_tb_grade3(USER_NAME,COURSE,SCORE) values(user_name, '英语', EN_SCORE)   
select user_name, CN_SCORE, MATH_SCORE, EN_SCORE from test_tb_grade2;   
commit;

别忘记commit操作，然后再查询TEST_TB_GRADE3，发现表中的数据就是列转成行了。