How to add a Single value as a Record add and update

Store procedure to add a single record it helps in terms of Contact Us where user will not enter more than one record in a table contact

create proc [dbo].[sp_ContactUs]
@desc varchar(MAx)
as
declare @temp as int
set @temp=(select count(*) from ContactUs)
if @temp=0
begin
insert into ContactUs values(1,@desc)
end
else
begin
update ContactUs set Descriptionn=@desc where id=1
end