What are supertype and subtype entities? Include an example. ...

[crobinson2013]

What are supertype and subtype entities? Include an example.
 
  What will be an ideal response?

Question 2

Explain the representation of a one-to-many strong entity relationship in a relational database design.
 
  What will be an ideal response?

[Kedrick2014]

Answer to Question 1

When instances of an entity can be categorized into different types with each type sharing some common characteristics while having certain characteristics that are unique to each type, the common attributes can be separated from the unique ones. This is represented in E-R diagrams through the use of supertype and subtype entities. The supertype entity class contains the attributes that are common to all of the subtypes. The subtype entity classes represent the different types, or categories, of the supertype. Only the attributes that are unique to a given subtype tend to be listed as the attributes of that subtype. Each subtype has a relationship with the supertype. All subtypes should have the same identifier as the supertype since they represent different perspectives of the same thing. As an example, consider VEHICLE (VIN, year, make) as a supertype, with subtypes CAR (VIN, model, seatingCapacity) and MOTORCYCLE (VIN, horsepower). All vehicles have VINs, a year, and a make. CARs additionally have a model and a seating capacity and MOTORCYCLES additionally have a horsepower rating.

Answer to Question 2

One-to-many relationships are represented by placing the primary key of the table on the one side of the relationship into the table on the many side of the relationship as a foreign key. The term parent refers to the table on the one side of a 1:N relationship, and the term child refers to the table on the many side of the 1:N relationship. Therefore, the rule for representing a one-to-many relationship can be summarized as Place the key of the parent table in the child table as a foreign key.