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  • 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
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