The Advanced objects                           
These objects are very important since they resolve very comlex filtering problems. For that particular purpose, three objects have been developed:
            1)       IN object
            2)       Advance extended object
            3)       OR object

The IN object                                                      
It is my opinion that we have learnt a lot about OOF and thus we shall start working with real objects. We have not yet managed to cover a very important segment of SQL command, that is the IN object.
As it is always easier to deal with examples, here comes one:

                     SELECT ;
                                    order. number_invoice ;
                                    order. order_date ;
                                    order.value_invoice ;
                                    order. payment ;
                                    customer. company_ name ;
                        FROM order, customer ;
                         WHERE (order.order_id   =  “   200” .OR. ;
                                        order.order_id   = “   300” .OR. ;
                                        order. order_id =  “   660” .OR. ;
                                        order. order_id =  “  1020”)

                                    or

SELECT ;
                                    order. number_invoice ;
                                    order. order_date ;
                                    order.value_invoice ;
                                    order. payment ;
                                    customer. company_ name ;
                        FROM order, customer ;
                         WHERE  ;
                                      order.order_id   IN (“   200”,”   300”,”   660”,”  1020” )

 Let’s look at vdf object once the form gets activated:

Take a look at this illustration! The image of IN object can be formed separately for the specific field. However, as for its dimensions, the object is relatively large covering larger space on the display. If we want to present two fields, this becomes a big problem due to the lack of the space on display. For each primary object, we also must have IN object since we do not know which filtering object is to be solved. Another problem is that each one of the objects will have to be filled in separately with the object qualities.