Sql Server：我如何使用别名unpivot？

Question

我知道你可以在pivot的列上使用别名，但我也想用别名unpivot。

select UserId 
,  ContactMethod 
,  ContactMethodValue 
from Users 
unpivot (
    ContactMethodValue for ContactMethod in 
    ( HomePhone  as [3000] 
    , OfficePhone as [3001] 
    , CellPhone  as [3002] 
    , Fax   as [3003] 
    , Website  as [3005] 
    ) 
) as unpvt 

但是，当我这样做时出现错误。

我一直能够实现我的最终目标的唯一方法是在select子句中使用case语句，这并不美观。

select UserId 
,  (case ContactMethod 
     when 'HomePhone' then 3000 
     when 'OfficePhone' then 3001 
     when 'CellPhone' then 3002 
     when 'Fax'   then 3003 
     when 'Website'  then 3005 
     end) as ContactMethod 
,  ContactMethodValue 
from Users 
unpivot (
    ContactMethodValue for ContactMethod in 
    ( HomePhone 
    , OfficePhone 
    , CellPhone 
    , Fax 
    , Website 
    ) 
) as unpvt 

有没有更好的方法？

Answer 1

您不能在UNPIVOT函数内部分配别名，因此您必须使用CASE表达式。

另一种方法是使用一个UNION ALL并直接将新值立刻道：

select userid, 3000 as ContactMethod, homePhone as ContactMethodValue 
from users 
union all 
select userid, 3001 as ContactMethod, OfficePhone as ContactMethodValue 
from users 
union all 
select userid, 3002 as ContactMethod, CellPhone as ContactMethodValue 
from users 
union all 
select userid, 3003 as ContactMethod, Website as ContactMethodValue 
from users 
union all 
select userid, 3005 as ContactMethod, homePhone as ContactMethodValue 
from users 

Answer 2

另一种方法是别名前的逆转置，如：

;with aliasedUsers as (
    select 
     UserId, 
     HomePhone  as [3000] 
     OfficePhone as [3001] 
     CellPhone  as [3002] 
     Fax   as [3003] 
     Website  as [3005] 
) 
select UserId 
,  ContactMethod 
,  ContactMethodValue 
from aliasedUsers 
unpivot (
    ContactMethodValue for ContactMethod in 
    ( [3000] 
    , [3001] 
    , [3002] 
    , [3003] 
    , [3005] 
    ) 
) as unpvt