Parameters not passin values to the report

Thanks Patrick,

This is what i did, in the query i added LASTNAME=@LASTNAME and then i created a PARAMETER and then a FILTER, my question is why do i need a filter. Secondly i want a functionality where if the user knows the last name he will enter and he will get the reocrd, but if he leaves the box without entering any value then he needs to see all the records, any idea please?

Thanks a lot!