Integer Parameter

I have a parameter field with a data type of int. I want the users to be able to select one or 'all' from the dropdown list. Is there a wildcard for a integer datatype?

Dropdown list example:

All Project Ids

1001

1002

1003

1004

In cases like this I will frequently use a NULL parameter to designate 'all'; can that work for you in this case? An example of this would be something like this:

declare @.example table (integerCol integer)
insert into @.example values (1001)
insert into @.example values (1002)
insert into @.example values (1003)
insert into @.example values (1004)

declare @.anIntegerParm integer
set @.anIntegerParm = null
set @.anIntegerParm = 1002

if @.anIntegerParm is null

select * from @.example

else

select * from @.example
where integerCol = @.anIntegerParm

-- When @.anIntegerParm is null:

-- integerCol
-- --
-- 1001
-- 1002
-- 1003
-- 1004

-- When @.anIntegerParm = 1002:

-- integerCol
-- --
-- 1002

select * from @.example
where @.anIntegerParm is null
or @.anIntegerParm is not null
and integerCol = @.anIntegerParm

-- integerCol
-- --
-- 1002