InfoPath Dev

How can I requery the data. I'm using a DataBase from microsoft sql server and in the each dropdownlist on change event contain a paramater that I passed to another dropdownlist to charge the Data. How Can I Requery??

I'm using cascading dropdown list and I want to refresh each dropdown in the on change event For example: I have two dropdown list, in the first one I have the following options A,B,C in the second one I have D,E,F if I select in the first DropDown option A I want to refresh the second one and so on with each DropDown. For now I put an empty ...