Conceptual Design Flashcards
What does an oval denote in an E/R Diagram?
Attribute
What does a rectangle denote in an E/R Diagram?
Entities
What does a diamond denote in an E/R Diagram
Relationship
What kind of attribute is underlined?
Key Attributes
What kind of attribute is double-circled?
Multi-valued Attributes
What kind of attribute is circled with a dotted line?
Derived Attributes
What kind of attribute is circled with a thick line?
Composite Attributes
Could a key value also be a special attribute?
No
What is a weak entity type?
Entities existence dependant on an identifying relationship
How can you identify weak entities?
Partial keys referring to foreign keys
How is cardinality represented?
1 or M above the linking relationship line
How is participation represented?
Single (partial) or double (total) linking relationship lines
How is multiplicity represented?
Upper and lower bound (U,L) above a linking line
What is a super key?
Attribute or set of attributes uniquely identifying a row
What is a candidate key?
Superkey with no subsets also being a superkey
What are the key attributes of a candidate key?
unqiueness and irreducibility
What is a primary key?
Candidate key used to identify a row
What is a foreign key?
Attribute within a relation matching candidate key of some relation
What is entity integrity?
Primary keys cannot be null
What is referrential integrity?
Foreign keys must match a candidate key of another row or must be null
