I've just published two new ADF Insider Essentials on You Tube. The first demonstrates how to set an attribute's default value to the value found in another entity object. This is a common use case where, for example, an employees default salary is the min salary for the job role, which is defined in the jobs table.
The second explains how to implement a total. Again a common use case where, for example, you want to display the total salary for a department (which of course is based on the total of all the relevant employee's salary).
These should be essential skills for anyone developing in the Oracle ADF world.