Joins at which layer ??

1) Where to define joins in FM layers, few says at database layer and few says at business layer.    Let us see where to do what - a)  data layer - making join at the data base layer makes more sense when you are modelling a relational data so that you only get those tables in the query which you really are using. This is called minimized query. b) business layer -  if you define joins here or I say if you don't define joins in the data layer then your data layer is free, on other layers you can redifne joins when need arise.