day05_行转列，列转行操作示例

create table TEST_TB_GRADE

(

ID NUMBER(10) not null,

USER_NAME VARCHAR2(20 CHAR),

COURSE VARCHAR2(20 CHAR),

SCORE FLOAT

);

insert into TEST_TB_GRADE values(1,'michael','语文',78);

insert into TEST_TB_GRADE values(2,'michael','数学',95);

insert into TEST_TB_GRADE values(3,'michael','英语',81);

insert into TEST_TB_GRADE values(4,'xiaoxiao','语文',97);

insert into TEST_TB_GRADE values(5,'xiaoxiao','数学',78);

insert into TEST_TB_GRADE values(6,'xiaoxiao','英语',91);

insert into TEST_TB_GRADE values(7,'zhangsan','语文',80);

insert into TEST_TB_GRADE values(8,'zhangsan','数学',55);

insert into TEST_TB_GRADE values(9,'zhangsan','英语',75);

insert into TEST_TB_GRADE values(10,'lisi','语文',87);

insert into TEST_TB_GRADE values(11,'lisi','数学',65);

insert into TEST_TB_GRADE values(12,'lisi','英语',75);

commit;

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：

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 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、列转行表结构： TEST_TB_GRADE2

Sql代码:

create table TEST_TB_GRADE2

(

ID NUMBER(10) not null,

USER_NAME VARCHAR2(20 CHAR),

CN_SCORE FLOAT,

MATH_SCORE FLOAT,

EN_SCORE FLOAT

);

insert into TEST_TB_GRADE2 values(1,'lisi',87,65,75);

insert into TEST_TB_GRADE2 values(2,'michael',78,95,81);

insert into TEST_TB_GRADE2 values(3,'xiaoxiao',97,78,91);

insert into TEST_TB_GRADE2 values(4,'zhangsan',80,55,75);

commit;





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

union

select user_name, 'MATH_SCORE' COURSE, MATH_SCORE as SCORE from test_tb_grade2

union

select 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

create table laowang(id number);

create table shuangshuang(id number);

create table xiaoming(id number);

create table dashi(id number);

insert all into ... select

insert all

into laowang

into shuangshuang

into xiaoming

into dashi

select OBJECT_ID from all_objects;

，首先需要先建一个表TEST_TB_GRADE3：

Sql代码:

create table TEST_TB_GRADE3

(

USER_NAME VARCHAR2(20 CHAR),

COURSE VARCHAR2(20 CHAR),

SCORE FLOAT

);

再执行下面的sql：

Sql代码:

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;

来自为知笔记(Wiz)