数据库行转列

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

createtable TEST_TB_GRADE  
  1. (  
  2.   ID        NUMBER(10) notnull,  
  3. USER_NAME VARCHAR2(20 CHAR),  
  4.   COURSE    VARCHAR2(20 CHAR),  
  5.   SCORE     FLOAT 
  6. ) 
[sql] view plaincopyprint?
  1. createtable TEST_TB_GRADE 
  2. ( 
  3.   ID        NUMBER(10) notnull, 
  4.   USER_NAME VARCHAR2(20 CHAR), 
  5.   COURSE    VARCHAR2(20 CHAR), 
  6.   SCORE     FLOAT 
  7. )  
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,  
  1.   sum(decode(t.course, '语文', score,null)) as CHINESE,  
  2.   sum(decode(t.course, '数学', score,null)) as MATH,  
  3.   sum(decode(t.course, '英语', score,null)) as ENGLISH  
  4. from test_tb_grade t  
  5. groupby t.user_name  
  6. orderby t.user_name 
[sql] view plaincopyprint?
  1. select t.user_name, 
  2.   sum(decode(t.course, '语文', score,null)) as CHINESE, 
  3.   sum(decode(t.course, '数学', score,null)) as MATH, 
  4.   sum(decode(t.course, '英语', score,null)) as ENGLISH 
  5. from test_tb_grade t 
  6. groupby t.user_name 
  7. orderby t.user_name  
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,  
  1.   sum(decode(t2.course, '语文', COUNTNUM,null)) as CHINESE,  
  2.   sum(decode(t2.course, '数学', COUNTNUM,null)) as MATH,  
  3.   sum(decode(t2.course, '英语', COUNTNUM,null)) as ENGLISH  
  4. from (  
  5.   select t.course,  
  6.          casewhen t.score  <60 then'00-60' 
  7.               when t.score >=60 and t.score <80  then'60-80' 
  8.               when t.score >=80 then'80-100'endas SCORE_GP,  
  9.          count(t.score) as COUNTNUM  
  10.   FROM test_tb_grade t  
  11.   groupby t.course,   
  12.         casewhen t.score  <60  then'00-60' 
  13.               when t.score >=60 and t.score <80  then'60-80' 
  14.               when t.score >=80 then'80-100'end 
  15.   orderby t.course ) t2  
  16. groupby t2.SCORE_GP  
  17. orderby t2.SCORE_GP 
[sql] view plaincopyprint?
  1. select t2.SCORE_GP, 
  2.   sum(decode(t2.course, '语文', COUNTNUM,null)) as CHINESE, 
  3.   sum(decode(t2.course, '数学', COUNTNUM,null)) as MATH, 
  4.   sum(decode(t2.course, '英语', COUNTNUM,null)) as ENGLISH 
  5. from ( 
  6.   select t.course, 
  7.          casewhen t.score  <60 then'00-60' 
  8.               when t.score >=60 and t.score <80  then'60-80' 
  9.               when t.score >=80 then'80-100'endas SCORE_GP, 
  10.          count(t.score) as COUNTNUM 
  11.   FROM test_tb_grade t 
  12.   groupby t.course,  
  13.         casewhen t.score  <60  then'00-60' 
  14.               when t.score >=60 and t.score <80  then'60-80' 
  15.               when t.score >=80 then'80-100'end 
  16.   orderby t.course ) t2 
  17. groupby t2.SCORE_GP 
  18. orderby t2.SCORE_GP  
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

createtable TEST_TB_GRADE2  
  1. (  
  2.   ID         NUMBER(10) notnull,  
  3.   USER_NAME  VARCHAR2(20 CHAR),  
  4.   CN_SCORE   FLOAT,  
  5.   MATH_SCORE FLOAT,  
  6.   EN_SCORE   FLOAT 
  7. ) 
[sql] view plaincopyprint?
  1. createtable TEST_TB_GRADE2 
  2. ( 
  3.   ID         NUMBER(10) notnull, 
  4.   USER_NAME  VARCHAR2(20 CHAR), 
  5.   CN_SCORE   FLOAT, 
  6.   MATH_SCORE FLOAT, 
  7.   EN_SCORE   FLOAT 
  8. )  
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   
  1. unionselect user_name, '数学' COURSE, MATH_SCORE as SCORE from test_tb_grade2   
  2. unionselect user_name, '英语' COURSE, EN_SCORE as SCORE from test_tb_grade2   
  3. orderby user_name,COURSE  
[sql] view plaincopyprint?
  1. select user_name, '语文' COURSE , CN_SCORE as SCORE from test_tb_grade2  
  2. unionselect user_name, '数学' COURSE, MATH_SCORE as SCORE from test_tb_grade2  
  3. unionselect user_name, '英语' COURSE, EN_SCORE as SCORE from test_tb_grade2  
  4. orderby user_name,COURSE   
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：

createtable TEST_TB_GRADE3    
  1.     (   
  2.       USER_NAME VARCHAR2(20 CHAR),    
  3.       COURSE    VARCHAR2(20 CHAR),    
  4.       SCORE     FLOAT    
  5.     )   
[sql] view plaincopyprint?
  1. createtable TEST_TB_GRADE3   
  2.     (  
  3.       USER_NAME VARCHAR2(20 CHAR),   
  4.       COURSE    VARCHAR2(20 CHAR),   
  5.       SCORE     FLOAT   
  6.     )    
create table TEST_TB_GRADE3  
    ( 
      USER_NAME VARCHAR2(20 CHAR),  
      COURSE    VARCHAR2(20 CHAR),  
      SCORE     FLOAT  
    )

再执行下面的sql：

insertall 
  1. into test_tb_grade3(USER_NAME,COURSE,SCORE) values(user_name, '语文', CN_SCORE)  
  2. into test_tb_grade3(USER_NAME,COURSE,SCORE) values(user_name, '数学', MATH_SCORE)  
  3. into test_tb_grade3(USER_NAME,COURSE,SCORE) values(user_name, '英语', EN_SCORE)  
  4. select user_name, CN_SCORE, MATH_SCORE, EN_SCORE from test_tb_grade2;  
  5. commit; 
[sql] view plaincopyprint?
  1. insertall 
  2. into test_tb_grade3(USER_NAME,COURSE,SCORE) values(user_name, '语文', CN_SCORE) 
  3. into test_tb_grade3(USER_NAME,COURSE,SCORE) values(user_name, '数学', MATH_SCORE) 
  4. into test_tb_grade3(USER_NAME,COURSE,SCORE) values(user_name, '英语', EN_SCORE) 
  5. select user_name, CN_SCORE, MATH_SCORE, EN_SCORE from test_tb_grade2; 
  6. commit;  
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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原文地址：https://www.cnblogs.com/zhoubinbin1991/p/2717761.html