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,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 ENGLISHfrom test_tb_grade tgroup by t.user_nameorder by t.user_name

case..when

select t.user_name,    sum(case when subject='语文' then score      else 0 end) as CHINESE,    sum(case when subject='数学' then score      else 0 end) as MATH,    sum(case when subject='英语'  then score      else 0 end) as ENGLISHfrom student_scoregroup by t.user_nameorder 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 ENGLISHfrom (  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' endorder by t.course ) t2group by t2.SCORE_GPorder by t2.SCORE_GP

二、列转行

1.1、初始测试数据

表结构： TEST_TB_GRADE2 ,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 unionselect user_name, 'MATH_SCORE' COURSE, MATH_SCORE as SCORE from test_tb_grade2 unionselect 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:  

1create table TEST_TB_GRADE3  

2( 

3      USER_NAME VARCHAR2(20 CHAR),  

4      COURSE    VARCHAR2(20 CHAR),  

5      SCORE     FLOAT  

6)

   
 再执行下面的sql： 
  Sql代码:  

view source

print?

1insert all

2into test_tb_grade3(USER_NAME,COURSE,SCORE) values(user_name, '语文', CN_SCORE)

3into test_tb_grade3(USER_NAME,COURSE,SCORE) values(user_name, '数学', MATH_SCORE)

4into test_tb_grade3(USER_NAME,COURSE,SCORE) values(user_name, '英语', EN_SCORE)

5select user_name, CN_SCORE, MATH_SCORE, EN_SCORE from test_tb_grade2;

6commit;

 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。