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oracle行转列和列转行

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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。

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