Relational Data Model Flashcards
Uses concept of mathematical relation as its building block and has theoretical basis in set theory and first-order predicate logic
Relational Data Model
Relational Data Model was first introduced by ______________ in ________
Edgar “Ted” F. Codd, 1970
“A Relational Model of Data for Large Shared Data Banks”
Relational Data Model represents the database as a collection of _____________
relations
Each __________ resembles a table of values wherein each “____” represents a fact that corresponds to a real-world entity or relationship
relation, row
The “_______” and “_______” names are used to help interpret them meaning of
the values of each “row”
table, column
In a relational data model, the attributes are represented as __________, and the tuple of values corresponding to an instance of a relation as a _______
column, row
The types of values that can appear in each attribute is the __________ of possible values
DOMAIN
Set of atomic values, Specify a data type from which the data values forming it are drawn
Domain
Relation Schema is denoted as
R(A1,A2, … An)
where R = Relation Name,
A = Attribute
Domain of Ai is denoted as
dom(Ai)
The number of attributes of its relation schema
Degree(or arity) of relation
What is the degree of the given relation below?
STUDENT(Student no, Name, Mobile phone, Address, Age, Gpa)
6 (6 attributes)
A ______________ (or just/simply relation) of the relation schema R denoted as r(R) is the set of n-tuples r = {t1,t2,…,t,}
relation state
Simply refers to all the rows stored in the table (that is the entire table)
A relation state at a given time is called the _________________________
current relation state
Notation for Relation State:
r(R)
ex: r(STUDENT), r(COURSE)
TRUE or FALSE:
A relation state is a subset of the Cartesian product of all domains of the attributes.
TRUE. A relation state is defined as A mathematical relation of degree n on the domains dom(A1), dom(A2), …, dom(An), which is a subset of the Cartesian product of
the domains:
r R ⊆ (dom A1 ⨯ dom A2 ⨯ … ⨯ dom An)
TRUE or FALSE:
Tuples in a relation DO NOT have a particular order
TRUE. The order of the rows doesn’t matter
TRUE or FALSE:
Values within a tuple do not have a particular order
FALSE. Order of values within a tuple (and of attributes) IS important. Although at a more abstract level, the order does not seem important as
long as the correspondence between them are maintained
TRUE or FALSE:
A value in a tuple can be composite or multivalued
FALSE. Each value in a tuple is an atomic value (Multivalued and Composite attributes are not allowed)
TRUE or FALSE:
NULL values are allowed and are used to represent values of attributes that are empty or zero.
FALSE. NULL does not have an inherent value. It is used to represent unknown, unavailable, or may not apply values.
The ________________ can be interpreted as a declaration or type of assertion
relation schema
A tuple (row) in a relation is also called as a _____________
FACT
Relational Model Constraints’ three main categories:
- Inherent model-based constraints
- Application-based constraints
- Schema-based constraints
Also called implicit constraints, Based on definition and characteristics of the model
Inherent model-based constraints
