declare @search_number int
set @search_number = 99 --찾을 숫자가 99라면..

;with dummy
as
(
        select 0 seq
        union all
        select seq + 1 from dummy
        where seq + 1 <= 1000
)
select 
	case when sign(seq - @search_number) > 0 then 'next' else 'prev' end as dir,
	case when sign(seq - @search_number) > 0 then min(seq) else max(seq) end as seq 
from dummy
where seq <> @search_number
group by sign(seq - @search_number)
order by sign(seq - @search_number)
option (maxrecursion 0);