CREATE FUNCTION [dbo].[Clienti] 
(  
        @Aperte as bit,
        @Chiuse as bit
)
RETURNS TABLE 
AS
RETURN 
(
  SELECT cl.Codice, cl.RagioneSociale
        FROM Clientela AS cl INNER JOIN Commesse AS co ON cl.Codice = co.CLIENTE
  GROUP BY cl.Codice, cl.RagioneSociale
        HAVING (CAST(COUNT(co.CHIUSURA) AS bit) = @Chiuse) AND (CAST(COUNT(co.CLIENTE) - COUNT(co.CHIUSURA) AS bit) = @Aperte)
)