i have those data set as shown below.
I would like to give to the users the possibility to select just with a click the "Cliente" where the "Importo Promessa di Pagamento" has an amount (so is different from null). How i can achieve this?
Are you trying to show all the values but ability to select only not null values?
Make a listbox for "Importo Promessa di Pagamento"
Right-click the listbox and choose Select All
Make a button and add an action that does Select in Field and select all.
Is this a table box? If you can use a straight table just add your
= IF(Sum(Importo Promessa di Pagamento) > 0, Sum(Importo Promessa di Pagamento))
Then supress 0 values in presentation tab.
Retrieving data ...