text: -- 8.5 Parameters
  
  drop procedure if exists get_clients_by_state;
  
  delimiter $$ 
  create procedure get_clients_by_state
  (
  	state char(2)
  )
  begin
  	select * from clients c where c.state = state;
  end $$ 
  
  delimiter ;
  
  call get_clients_by_state('ca');
  -- call get_clients_by_state(''); , this returns error
  
  -- exercise
  
  drop procedure if exists get_invoices_by_clients;
  
  delimiter $$
  
  create procedure get_invoices_by_clients
  (
  client_id int
  )
  begin
  	select * from invoices i
      where i.client_id = client_id;
  end $$
  
  delimiter ;
  
  call get_invoices_by_clients(1);