Question

This statement errors if there are no rows in the select statment (select top 1…)

update tHomePageWorking 
set nColumn = 2, 
    nPosition = ((select top 1 nPosition 
                  from tHomePageWorking 
                  where nColumn = 2 
                  order by nPosition desc) + 1
                 ) 
where nPosition = 1 and nColumn = 1

Is there a way to test the count of this statement and default to 1 if no records found?

select top 1 nPosition 
from tHomePageWorking 
where nColumn = 2 
order by nPosition desc

Answer 1

I think the COALESCE function wil lsolve your problem.
It will return the first non-null argument:

update tHomePageWorking 
set nColumn = 2, 
    nPosition = COALESCE (
                 ((select top 1 nPosition 
                  from tHomePageWorking 
                  where nColumn = 2 
                  order by nPosition desc) + 1
                 ) 
                 ,1)
where nPosition = 1 and nColumn = 1