

Effect of functional dependencies:


Example:
Employee2(SSN, FName, LName, DNumber, DName, MgrSSN) Functional dependency: DNumber → DName 


Employee2(SSN, FName, LName, DNumber, DName, MgrSSN) Functional dependencies: SSN → FName, LName, DNumber, DName, MgrSSN DNumber → DName, MgrSSN 
The complete list of functional dependencies is actually as follows:
SSN → FName SSN → LName SSN → DNumber SSN → DName SSN → MgerSSN DNumber → DName DNumber → MgrSSN 
R_{1}(SSN, FName, LName, DNumber) R_{2}(DNumber, DName, MgrSSN) 
Now consider whether each of the (original) functional dependencies was preserved:
SSN → FName preserved in R_{1} SSN → LName preserved in R_{1} SSN → DNumber preserved in R_{1} SSN → DName preserved in R_{1} SSN → MgerSSN preserved in R_{1} DNumber → DName preserved in R_{2} DNumber → MgrSSN preserved in R_{2} 

TJS(Teacher, Subject, Student) Functional dependencies: Student, Subject → Teacher Teacher → Subject 
The complete list of functional dependencies is as follows:
Student, Subject → Teacher Teacher → Subject 
R_{1}(Student, Teacher) R_{2}(Teacher, Subject) 
Now consider whether each of the (original) functional dependencies was preserved:
Student, Subject → Teacher lost !!! (Student, Subject are not found in same relation together !) Teacher → Subject preserved in R_{2} 






