Hi,

 

If you are using Static LOVs then follow the below steps to Add ALL to your paramter.

 

Double click on Parameter and It will open Edit Parameter window, in Value section you can able to see Click here to add item, click on that and Write "ALL"
Beside actions button, Up and Down arrow symbols will visible. use up botton to show "ALL" on first place.
Then click on Ok

In the Select Expert dialog box, press the Show Formula button, and at the bottom enter the following formula:

        If {?Staff_Name} = "All"  then True else {database field_Staff_name} = {?Staff Country}

 

--Praveen G