Ms sql pivot unpivot

--建表
create table dbo.orders
( orderid int not null primary key nonclustered,
  orderdate datetime not null,
  empid int not null,
  custid varchar(5) not null,
  qty  int not null)
--插入数据
insert into orders values(30001,'',3,'a',10)
insert into orders values(10001,'',1,'a',12)
insert into orders values(10005,'',1,'b',20)
insert into orders values(40001,'',4,'a',40)
insert into orders values(10006,'',1,'c',14)
insert into orders values(20001,'',2,'b',12)
insert into orders values(40005,'',4,'a',10)
insert into orders values(20002,'',2,'c',20)
insert into orders values(30003,'',3,'b',15)
insert into orders values(30004,'',3,'c',22)
insert into orders values(30007,'',3,'d',30)

--数据。
select custid,year(orderdate) as orderdate ,qty from orders   order by custid

custid orderdate   qty
------ ----------- -----------
a      2002        10
a      2002        12
a      2003        40
a      2004        10
b      2004        15
b      2003        12
b      2002        20
c      2002        22
c      2003        14
c      2004        20
d      2002        30
(11 行受影响)

--转阿转。
select custid,sum(case when orderdate=2002 then qty end) as [],
                     sum(case when orderdate=2003 then qty end) as [],
                     sum(case when orderdate=2004 then qty end) as []
from ( select custid,year(orderdate) as orderdate ,qty from orders  ) as d group by custid;

custid 2002        2003        2004
------ ----------- ----------- -----------
a      22          40          10
b      20          12          15
c      22          14          20
d      30          NULL        NULL
警告: 聚合或其他 SET 操作消除了空值。
(4 行受影响)

--行转列
select *  from (select custid,year(orderdate) as orderyear,qty from dbo.orders) as d
pivot (sum(qty) for orderyear in ([],[],[])) as p;

custid 2002        2003        2004
------ ----------- ----------- -----------
a      22          40          10
b      20          12          15
c      22          14          20
d      30          NULL        NULL
 (4 行受影响)

--反转。
select custid,orderyear,qty from pvtt unpivot ( qty for orderyear in ([],[],[])) as u;

 custid orderyear                                                                                                                        qty
------ -------------------------------------------------------------------------------------------------------------------------------- -----------
a      2002                                                                                                                             22
a      2003                                                                                                                             40
a      2004                                                                                                                             10
b      2002                                                                                                                             20
b      2003                                                                                                                             12
b      2004                                                                                                                             15
c      2002                                                                                                                             22
c      2003                                                                                                                             14
c      2004                                                                                                                             20
d      2002                                                                                                                             30
(10 行受影响)

--动态反转。注意@b变量要放在括号里，否则报不是有效的标识符
declare @a varchar(4000),@b varchar(4000)
set @a=''
select @a=@a+'],['+cast(a as varchar(10)) from (select distinct year(orderdate) as a from orders) as b
set @a=right(@a,len(@a)-2)+']'
set @b='select custid,orderyear,qty from pvtt unpivot (qty for orderyear in ('+ @a +')) as c'
exec (@b)

custid orderyear                                                                                                                 qty
------ ----------------------------------------------------------------------------------------
a      2002                                                                                                                             22
a      2003                                                                                                                             40
a      2004                                                                                                                             10
b      2002                                                                                                                             20
b      2003                                                                                                                             12
b      2004                                                                                                                             15
c      2002                                                                                                                             22
c      2003                                                                                                                             14
c      2004                                                                                                                             20
d      2002                                                                                                                             30
(10 行受影响)

--动态反转,注意DISTINCT引用否则则提示多次引用列。
declare @a varchar(4000),@b varchar(4000)
set @a=''
select @a=@a+aa from (select distinct (select '['+cast ( a as varchar(10))+'],' as [text()] from (select distinct year(orderdate) as a  from orders
) as a3 for xml path('')) as aa from (select distinct year(orderdate) as a  from orders
) as a2) as c
set @a=left(@a,len(@a)-1)
set @b='select custid,orderyear,qty from pvtt unpivot (qty for orderyear in ('+ @a +')) as c'
exec (@b)

custid orderyear                                                                                                                 qty
------ --------------------------------------------------------------------------------------
a      2002                                                                                                                             22
a      2003                                                                                                                             40
a      2004                                                                                                                             10
b      2002                                                                                                                             20
b      2003                                                                                                                             12
b      2004                                                                                                                             15
c      2002                                                                                                                             22
c      2003                                                                                                                             14
c      2004                                                                                                                             20
d      2002                                                                                                                             30
(10 行受影响)

--通过系统视图（INFORMAT_SCHEMA.COLUMNS）拉列表。
declare @a  as table( y int  not null primary key );
declare @cols as nvarchar(max)
declare @sql as  nvarchar(max)
set @cols=stuff(
(select N','+quotename(y) as [text()] from
(select column_name as y  from INFORMATION_SCHEMA.COLUMNS
where table_schema=N'dbo' and table_name=N'pvtt'  and column_name not in (N'custid')) as y
order by  y for xml path('')),1 ,1 ,N'');
set @sql=N'select custid,orderyear,qty from dbo.pvtt unpivot(qty for  orderyear in ('+@cols+N')) as u;';
exec sp_executesql @sql

custid orderyear                                                                                                                 qty
------ -------------------------------------------------------------------------------------
a      2002                                                                                                                             22
a      2003                                                                                                                             40
a      2004                                                                                                                             10
b      2002                                                                                                                             20
b      2003                                                                                                                             12
b      2004                                                                                                                             15
c      2002                                                                                                                             22
c      2003                                                                                                                             14
c      2004                                                                                                                             20
d      2002                                                                                                                             30
(10 行受影响)