if exists ( select  *
            from    sys.objects
            where   object_id = object_id(N‘dbo.nvl‘) and type  = N‘FN‘)
begin
    drop function [dbo].[nvl];
end
go
create function dbo.nvl(@check_value sql_variant ,@replace_value sql_variant )  
returns sql_variant
as
begin
   
    return isnull(@check_value,@replace_value);
end
go

select dbo.nvl(null,‘sfs‘)
select dbo.nvl(null,1)
select dbo.nvl(null,getdate())
select dbo.nvl(1111,100000000)

sqlserver創建接受任何類型的nvl