nvarchar列在sql中查找上一个日期

Question

I have followin table schema

declare @temp table  
 (
   id int identity(1,1) not null,
   nod nvarchar(50) 
 )

in which nod column have following data

insert into @temp select 'N/A'
 insert into @temp select 'N/A'
 insert into @temp select '5'
 insert into @temp select 'N/A'
 insert into @temp select '7'
 insert into @temp select 'N/A'
 insert into @temp select '31'
 insert into @temp select '15'

i want that select stament shoud give me result on following basis

if nod value 'N/A' then it should show 'N/A'

or if there any numeric value like 5,15,31 then it should show getdate()-nod date date column

I have tried following but fail to minus the days and also represent 'N/A' when 'N/A' in that nvarchar column

 select  DATEADD(dd,case nod when 'N/A' then 0 else nod end,GETDATE()) from @temp

sql fiddle is here

Answer 1

The following query would return a VARCHAR(50) column that contains either 'N/A' or now - nod date as varchar.

SELECT
     CASE nod
         WHEN 'N/A' THEN 'N/A'
         ELSE CONVERT(VARCHAR(50), 
                      DATEADD(dd, 
                              -1 * CONVERT(INT, nod), 
                              GETDATE()
                             )
                     ) 
     END
FROM @temp