Entity Relationship Model Flashcards
1
Q
give the 3 stages of database design
A
data requirements
conceptual model
logical model
2
Q
what is a conceptual design
A
ER model
simple, formal, flexible
3
Q
what entity types are there
A
strong
weak
4
Q
what attribute types are there (8)
A
composite/simple
single values/multivalued
stored/derived
null valued
complex valued
5
Q
what types of relationships are there
A
normal
identifying
6
Q
describe keys, including strong and weak keys
A
uniquely identifiable attribute of an entity
strong- unique globally
weak- unique locally. No natural assigned key
7
Q
describe cardinality
A
a cardinality ratio constraint specifies the maximum number of relationship instances that an entity can participate in
8
Q
describe a participation constraint
A
if participation is total, every entity in the total must participate
