>I dragged but it won't create the relation
> Does relation in the database have the same behaviour
> as in the dataenvironment ?

No. Relations in DE is independent from database relations. They're not persistent and could be done from any field to an index field. ie: You could relate orders.cust_id to customer.cust_id (reverse of DBC - from customer to orders).
As per dragging, I was not always successfull creating with mouse too. Just create any one you can with mouse, click on relation (connector line) and edit properties.
Cetin