SQL 行转列，列转行, 带SQL脚本方便大家验证.

目录结构如下：

• 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：

具体的实现sql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。