I am playing with moving my free tables into a DBC...(slow adopter here)

So I added my tables in the DBC and edited certain indexes to become Primary Keys, and then dragged from that PK to a Regular Index in the child tables to create relationships....

So now, how do I use those relationships in forms in my app. I open the database, and when I USE the tables, the relationships do not appear. If I must still do SET RELATION code, what have I gained by adding the relationship in my DBC?