Entity Relationship Modeling Flashcards
What are the main components of a database?
Entities, attributes, relationships
What is one-to-many?
1:M, each tuple in the entity can be related to many tuples in the relating entity
What is one-to-one?
1:1, each tuple in one entity is linked to one and only one other tuple in another entity
What is many-to-many?
M:N, many instances of one entity are associated with many instances of another entity
What is an associative entity?
also know as composite or bridge entity. create associative entity with two options, inherits its primary key…and has its own primary key as well as foreign keys…
What is multiplicity?
specification of the range of cardinality values for a particular set. established by the business rules
What is cardinality?
expresses the min and max number of entity occurrences associated w/ one occurrence of the related entity
What is participation?
Determines whether all or only some entity occurrences participate in a relationship
What is a primary key?
Most important characteristic of an entity. Uniquely identifies an entity instance or tuple within an entity.
What is a foreign key?
Attribute in one entity matches the primary key in another entity proving a link b/w the two entities
What are the three types of relationships?
Unary, binary, ternary
What is an unary relationship?
A relationship existing within a single entity
What is a binary relationship?
Exists when two entities are associated in a relationship
What is a ternary relationship?
Relationship implies an association among three different entities
What is homonym?
Same name is used to label different attributes
