Raggruppamenti per due colonne

USE tempdb;

CREATE TABLE dbo.foo(
negozio char(3) NOT NULL,
data date NOT NULL,
numeroscontrino int NOT NULL,
codiceprodotto varchar(50) NOT NULL, 
area char(3) NOT NULL,
category char(3) NOT NULL
);

INSERT dbo.foo VALUES
      ('005', '2009-09-02', 1, '00010251 Du Duplarin L 90 ml', 'A01', 'C20')
    , ('005', '2009-09-02', 1, '00001787 Mx Blucarbon Carbone Attivo', 'A02', 'C20')
    , ('005', '2009-09-02', 2, '00006422 Pd Tappetini Assorbenti 60x90', 'A02', 'C10')
    , ('005', '2009-09-02', 3, '00000901 Go Gold Trota alla Marinara 85 g', 'A01', 'C50')
    , ('005', '2009-09-02', 3, '00004335 Go Gold Coniglio e Fegato 85 g', 'A01', 'C50')
    , ('005', '2009-09-02', 3, '00003211 Sh Cat Creazioni c/ Oca 100 g', 'A01', 'C50')
    , ('005', '2009-09-02', 3, '00003212 Sh Cat Creazioni c/ Agnello 100 g', 'A01', 'C50')
    , ('005', '2009-09-02', 3, '00004510 Al Cat Nature Pollo con Formaggio 70 g', 'A01', 'C50');

SELECT area, category, COUNT(*) AS Numero
FROM dbo.foo
GROUP BY area, category;

/* Output:

area category Numero
---- -------- -----------
A02  C10      1
A01  C20      1
A02  C20      1
A01  C50      5

(4 row(s) affected)

*/

DROP TABLE dbo.foo;

>Grazie!