Entity Relationship Model Flashcards
The _______-________ model is a notation for describing schemas in databases
entity-relationship
The ER model is a high-level ______
sketch
A DB design is called a ER ______
diagram
ER models are converted to relational DB ______
schemas
Later in the DB design phase, the _____ model is transformed into a ____ model
conceptual, logical
The _________ process removes redundancies in data or updates anomalies in the DB design
normalization
The ______ representation of the DB model usually differs from the logical representation
physical
An _____ is a thing or object
entity
An entity set is a ______ of similar entities
collection
An attribute is a ______ of an entity set
property
An _______ is a simple value, like an int or char string
attribute
In ER diagrams, an entity set is a _______
rectangle
In ER diagrams, _______ are an oval with a line to its entity set
attributes
In ER diagrams, a relationship is represented as a ______ with lines to each of the two or more entity sets involved
diamond
A ———–> B indicates what? What is the term for this?
A is owned by at most one B. The term is “uniqueness constraint”
The value of an entity set is the set of _______ that belong to it
entities
The value of a relationship is a _________ set
relationship
A relationship set is a set of tuples with one ______ for each related entity set
component
A _______ constraint imposes lower and upper bounds on the number of connections between entities E and F
cardinality
What are the 3 different multiplicity restrictions we can have for a binary relationship?
Many-to-one, one-to-one, and many-to-many
In a __________ relationship, each entity of the first set is connected to at most one entity of the second set
Many-to-one
You can show a _______ relationship in an ER diagram by an arrow entering the one side
many-to-one
You can show a ________ relationship in an ER diagram with an arrow entering both entity sets
one-to-one
A regular arrow in an ER diagram shows a relation of ______ _____ _____
at most one
A rounded arrow in an ER diagram shows a relation of ______ _____
exactly one
An “Is-A” relation declares that every A entity is also a _ entity
B
A candidate key must be a _____ identifier and must be ______
unique, minimal
