SQL Server 中带有 while 循环的用户定义函数

I am asked to create a user defined function in SQL Server to returns the following pattern (for example, if the input = 5):

*****
 ****
  ***
   **
    *

这是我的代码:

alter function udf_star (@input int)
returns varchar (200)
as 
begin 
    declare @star int 
    set @star = @input 

    declare @space int 
    set @space = 0

    while @star > 0
    begin 
        declare @string varchar (200)
        set @string = replicate (' ', @space) + replicate ('*', @star)

        set @star = @star - 1
        set @space = @space + 1  
    end 

    return @string 
end 

当我执行函数时

select dbo.udf_star (5)

它只显示

'    *'

(4 个空格 + 1 颗星)；谁能指出我应该如何更正语法?

CREATE FUNCTION [dbo].[tvf-Star] (@Input int)
Returns Table 
As
Return (  

Select Top (@Input) 
       Stars = replicate(' ',@Input-N)+replicate('*',N)
 From ( Select Top (@Input) N=Row_Number() Over (Order By (Select NULL)) From master..spt_values n1 ) A
 Order By N Desc
)

Select * from [dbo].[tvf-Star](5)

Stars
*****
 ****
  ***
   **
    *