Question 1 Define each of the following terms. In addition, provide an example of each term.
a. Entity Set - A collection of like entities. Example: If a customer is an entity, then the entity set would be a collection of two or more customers.
b. Entity Instance - Each row in the relational table. Example: A row of information beginning with the entity itself and showing the relations of that specific entity and none other.
c. Attribute - A characteristic of an entity. Example: The information used to describe the entity. If the entity is CLIENT, then the attributes would probably contain things like ‘address’, or ‘name’ or other specific bits of information.
d. Connectivity - This is the name given as a label for the different connection types, one to one, one to many, and many to many. Example: If the Relationship is ...view middle of the document...
The foreign key would be the attribute that allows somebody to
g. Associative Entity (Composite Entity) - This is an entity that seeks to convert a many to many relationship to a 1 to many relationship by either compiling foreign keys or creating a new primary key on a new table. Example: Creating a table that tracks 2 or more foreign keys to identify a third attribute.
h. Cardinality Constraint - This a command used to restrict information based on a number value or range. Example: doing a search for all prices higher than $5 but lower than $10.
i. Weak Entity - This is a two-part definition. This entity must have the entity it is related to be present in order to exist, and must have a primary key that is partially or completely derived from the entity it’s related to. Example: An example of this is if an entity is a person buying a car and they need a cosigner. They could not get the car without that second signature. Both people become entities, and the person needing the cosign is the weak entity.
j. Business Rule - This is a description of a policy or parameter within an organization and are used to define entities, attributes, relationships, and constraints. Example: “A student may take 5 classes.” This rule will only allow a student (identified by a PK) to enroll in 5 courses (identified by a PK for classes) and will not allow any more enrollments.
Question 2 Business Rules
Database - Unit
ONE Database may Track MANY Units [M]
ONE Unit can be tracked by ONE Database [1]
Database 1:M Units.
Question 3 Entity Relationship Diagram
Question 4 Primary Key / Foreign Key Placement
Entity Set | Primary Key Attribute(s) | Foreign Key Attributes(s) |
Publisher | Publisher_ID | |
Volume | Volume_ID, Volume_Name | ISBN-13, ISBN-10, BOOK_Title |
Book | ISBN-13, ISBN-10, Book_Title | |
Book-Author | Author_ID | Author_Lastname, Author_Firstname |
Author | Author_Lastname Author_FirstnameAuthor_ID | |
Country | ID | |
