目录结构如下：
[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
- )
- 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
- 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
- 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
- )
- 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
- 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
- )
- 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;
- 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。
本文连接：http://sjsky.iteye.com/blog/1152167
数据库 行转列 列转行详解,布布扣,bubuko.com
数据库 行转列 列转行详解
原文：http://www.cnblogs.com/shadowwalker/p/3726440.html
