What is NDNQI and how was is it used in the study by Garrard et al.?

Fall Code

What is NDNQI and how was is it used in the study by Garrard et al.?

What is the primary key for the Patient Table?What is the foreign key for the Patient Table? What is the primary key for the Fall Table?

Assume that each fall code can be used for multiple patients and each patient can receive only one fall code. What kind of relationship exists between the Fall Table and Patient Table?