Hi Hülya,
If you're reporting against a RDBMS, here's what you need to:
1) Go to Database Expert > Expand the Connection Name > Double-click Add Command and create a SQL query.
2) Let's say you're trying to create a prompt for the field 'Country', the query would look like this:
select table.country from table
UNION
select 'ALL' from table
3) Go to the Links tab and delete any links between this Command object and the tables already in there
4) Go to the Field Explorer > Create a new parameter. Set its type as Dynamic and from the Value options, choose the Country field from the Command Object
5) Add a Record Selection formula like this:
{?parameter_name} = 'ALL' OR
{?parameter_name} = {Country_field}
Another way to do this if you're using CR 2008 or higher is to make the existing prompt 'Optional'. So, if you do not wish to follow the 1st method, try this:
1) Go to the Field Explorer > Edit the prompt > Scroll down and look for the option 'Optional Prompt'. Set that to True.
2) Go to the Record Selection formula and modify it to:
not(hasvalue({?Parameter_Name})) OR
{?Parameter_Name} = {Country_field}
This method will not show the text 'All' in the prompt values, however it will let you run the report without selecting any values from the list. If you don't select any values from the list, the report will show all the records.
Hope this helps.
-Abhilash