reporting services - Selecting either one or ALL the values in a parameter in SSRS 2008 R2 -

i working on reporting project in ssrs. have parameter called 'customer'. values parameter populated sql query. want restrict parameter such user should able select either one customer or all customers. there should not possibilities select either 2 or 3 customers.

have option in parameter list called all customers ordered sits @ top of parameter list.

if manually adding parameter options, ordering easy. if data-driven can union all in parameter value dataset correct order:

select <unique value matches customer id type> value       ,'all customers' label       ,1 sortorder  union  select customerid value       ,customername label       ,2 sortorder customertable order sortorder         ,label 

and in query need add logic handles new all value:

select columns tables customerid = @customer    or @customer = <unique value matches customer id type>