MIS 3353 EXAM 2 REVIEW | STUDY GUIDE
Rule 1: Nouns / Verbs - Answers - Identify potential entities in the domain. Each noun
typically becomes an entity within the ERD.
Attributes, help define the relationships between these entities. The verbs describe
interactions or associations that naturally exist between the entities.
Rule 2: Cardinality - Answers - This defines the number of instances of one entity that
can or must be associated with each instance of another entity. Are crucial for
understanding the data model's dynamics.
Examples: One-to-One, One-to-Many, or Many-to-Many
Rule 3: Primary Key (PK) - Answers - Each entity in an ERD must have a primary key,
which uniquely identifies each instance of the entity. This key is essential for ensuring
that every record within a table can be uniquely accessed without ambiguity.
Cannot be null, or change over time.
Rule 4: Foreign Key (FK) - Answers - A field (or collection of fields) in one table, that
uniquely identifies a row of another table.
Used to establish and enforce a link between the data in two tables, reflecting the
relationships identified by verbs.
Rule 5: Associative Entities (Many-to-Many) - Answers - Used when a many-to-many
relationship exists between two entities. An associative entity converts this many-to-
many relationship into two one-to-many relationships.
It typically holds the Foreign Keys (FK) from each of the entities involved in the
relationship as well as other attributes pertinent to the relationship.
Type of history that contains a "Date."
Rule 6: Sub-types/Super-types - Answers - Sub-types can exist when instances share
some, but not all attributes OR a set of instances have a unique relationship.
Belongs to more than 1 sub-type = Overlap
Belongs to only 1 sub-type = Disjoint
1 line = Partial Specialization
2 lines = Total Specialization
Rule 1: Nouns / Verbs - Answers - Identify potential entities in the domain. Each noun
typically becomes an entity within the ERD.
Attributes, help define the relationships between these entities. The verbs describe
interactions or associations that naturally exist between the entities.
Rule 2: Cardinality - Answers - This defines the number of instances of one entity that
can or must be associated with each instance of another entity. Are crucial for
understanding the data model's dynamics.
Examples: One-to-One, One-to-Many, or Many-to-Many
Rule 3: Primary Key (PK) - Answers - Each entity in an ERD must have a primary key,
which uniquely identifies each instance of the entity. This key is essential for ensuring
that every record within a table can be uniquely accessed without ambiguity.
Cannot be null, or change over time.
Rule 4: Foreign Key (FK) - Answers - A field (or collection of fields) in one table, that
uniquely identifies a row of another table.
Used to establish and enforce a link between the data in two tables, reflecting the
relationships identified by verbs.
Rule 5: Associative Entities (Many-to-Many) - Answers - Used when a many-to-many
relationship exists between two entities. An associative entity converts this many-to-
many relationship into two one-to-many relationships.
It typically holds the Foreign Keys (FK) from each of the entities involved in the
relationship as well as other attributes pertinent to the relationship.
Type of history that contains a "Date."
Rule 6: Sub-types/Super-types - Answers - Sub-types can exist when instances share
some, but not all attributes OR a set of instances have a unique relationship.
Belongs to more than 1 sub-type = Overlap
Belongs to only 1 sub-type = Disjoint
1 line = Partial Specialization
2 lines = Total Specialization
