Person
PersonID (PK)| {Person Attributes}

Employee
EmployeeID(PK)| PersonID (FK)| {Employee Attributes}

Customer
CustomerID(PK)| PersonID (FK)| {Customer Attributes}

PersonID --> CustomerID
PersonID --> EmployeeID

PersonID --> CustomerID --> {Customer Attributes}
PersonID --> EmployeeID --> {Employee Attributes}

Person
PersonID (PK)| PersonName

Employee
PersonID (PK)| EmployeeID | {Employee Attributes}

Customer
PersonID (PK)| CustomerID | {Customer Attributes}

PersonID --> CustomerID --> {Customer Attributes}
PersonID --> EmployeeID --> {Employee Attributes}

Person
PersonID (PK)| PersonType (Employee/Customer) | {Person Attributes}

Employee
PersonID (PK)| {Employee Attributes}

Customer
PersonID (PK)| {Customer Attributes}

Person
PersonID (PK)| {Person Attributes}

Employee
PersonID (PK)| {Employee Attributes}

Customer
PersonID (PK)| {Customer Attributes}