oracle 行转列和列转行

一、行转列

1.1、初始测试数据

表结构：TEST_TB_GRADE

Sql代码:

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：

Sql代码:

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：

      

具体的实现sql如下：
Sql代码:

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
Sql代码: 

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：
Sql代码: 

select user_name, 'CN_SCORE' COURSE , CN_SCORE as SCORE from test_tb_grade2  
union 
select user_name, 'MATH_SCORE' COURSE, MATH_SCORE as SCORE from test_tb_grade2  
union 
select user_name, 'EN_SCORE' 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：

Sql代码: 

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

  
 再执行下面的sql：
  Sql代码: 

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。