Totale dei clienti

[kodode]

SELECT form1.idcliente, form2.idcliente, form1.cliente, SUM ( form2.importo ) AS tot_imporot FORM form1, form2 WHERE form1.idcliente = form2.idcliente GROUP BY form2.idcliente

prova a vedere cosi... se non funzia potresti provare con left join :

SELECT form1.idcliente, form2.idcliente, form1.cliente, SUM ( form2.importo ) AS tot_import FORM form1 LEFT JOIN form2 ON form1.idcliente = form2.idcliente GROUP BY form2.idcliente