Question

In an E-R Diagram how would i model two many-to-many relationships

 FACILITY
 Facility_ID
 Name
 etc

 PHYSICIAN
 Physician_Id
 Name
 etc

 PATIENT
 Patient_Id
 Name
 etc

M:N – where a Facility can staff many Physicians and a Physician can be enmployed by many facilities
M-N – where a Patient can be treated by many Physicians and a Physicians can treat many patients’

Answer 1

This is a common relational design problem. To solve it, you create so called a junction table or an associative entity.

Here are some helpful explanations with examples that should help you relate to yours:

http://en.wikipedia.org/wiki/Associative_Entities

http://en.wikipedia.org/wiki/Junction_table

In your case, you would probably have:

 Facilty_Physican
 ----------------
 Facility_ID
 Physician_Id

and

 Physican_Patient
 ----------------
 Physician_Id
 Patient_Id

You may also find that sometimes in data model optimizations and depending on the balance of the relationship some denormalize junction tables.