create database arron  
go  
use arron  
go  
  
-- createTable init Data  
create table students (  
  name varchar(25),  
  class varchar(25),  
  grade int  
)  
insert into students values ('張三','語文',20)  
insert into students values ('張三','數學',90)  
insert into students values ('張三','英語',50)  
insert into students values ('李四','語文',81)  
insert into students values ('李四','數學',60)  
insert into students values ('李四','英語',90)  
  
-- solution1  
select * from students   
pivot(   
max(grade)   
FOR [class] IN ([語文],[數學],[英語])  
) AS pvt  
  
  
-- solution2 相當於自連線  
  
select A.Name,A.grade as 語文,B.grade as 數學,C.grade as 英語  
from students A,students B,students C  
where A.Name=B.Name and B.Name=C.Name  
and A.class='語文' and B.class='數學'  
and C.class='英語'  
  
-- solution3   
select name,  
max(case when s.class='語文' then s.grade end) as 語文,  
max(case when s.class='數學' then s.grade end) as 數學,  
max(case when s.class='英語' then s.grade end) as 英語  
 from students s group by name  
  
  
--在有id 的情況下  
create table students2 (  
  id int primary key identity(1,1),  
  name varchar(25),  
  class varchar(25),  
  grade int  
)  
  
insert into students2 values ('張三','語文',20)  
insert into students2 values ('張三','數學',90)  
insert into students2 values ('張三','英語',50)  
insert into students2 values ('李四','語文',81)  
insert into students2 values ('李四','數學',60)  
insert into students2 values ('李四','英語',90)  
  
-- 原先的solution1(有問題)  
select * from students2   
pivot(   
max(grade)   
FOR [class] IN ([語文],[數學],[英語])  
) AS pvt  
-- 原先的solution2 (ok)  
select A.Name,A.grade as 語文,B.grade as 數學,C.grade as 英語  
from students A,students2 B,students2 C  
where A.Name=B.Name and B.Name=C.Name  
and A.class='語文' and B.class='數學'  
and C.class='英語'  
-- 原先的solution3 （ok）  
select name,  
max(case when s.class='語文' then s.grade end) as 語文,  
max(case when s.class='數學' then s.grade end) as 數學,  
max(case when s.class='英語' then s.grade end) as 英語  
 from students s group by name  
  
  
--unpivot 函式使用  
create table test1(id int,name varchar(20), Q1 int, Q2 int, Q3 int, Q4 int)  
insert into test1 values(1,'a',1000,2000,4000,5000)  
insert into test1 values(2,'b',3000,3500,4200,5500)   
  
--實現的sql  
select * from test1  
  
select id ,[name],[jidu],[xiaoshou] from test1  
unpivot  
(  
 xiaoshou for jidu in  
 ([q1],[q2],[q3],[q4])  
)  
as f  
  
--- 以下的sql 可以替換上面的sql  
select id,[name],  
jidu='Q1',  
xiaoshou=(select Q1 from test1 where id=a.id)  
from test1 as a  
union  
select id,[name],  
jidu='Q2',  
xiaoshou=(select Q2 from test1 where id=a.id)  
from test1 as a  
union  
select id,[name],  
jidu='Q3',  
xiaoshou=(select Q3 from test1 where id=a.id)  
from test1 as a  
union  
select id,[name],  
jidu='Q4',  
xiaoshou=(select Q4 from test1 where id=a.id)  
from test1 as a