The relational database model

Question 1

predicate logic

Answer 1

used extensively in mathematics to provide a framework in which an assertion can be verified as either true or false

Question 2

set theory

Answer 2

a part of mathematical science that deals with sets, or groups of things, and is used as the basis for data manipulation in the relational model

Question 3

tuple

Answer 3

in the relational model, a table row

Question 4

attribute domain

Answer 4

in data modelling, the construct used to organize and describe an attribute’s set of possible values

Question 5

primary key

Answer 5

an attribute or combination or attributes that uniquely identifies any given row

Question 6

a key

Answer 6

consists of one or more attributes that determine other attributes

Question 7

determination

Answer 7

the state in which knowing the value of one attribute makes it possible to determine the value of another

Question 8

functional dependence

Answer 8

the value of one or more attributes determines the value of one or more pother attributes

Question 9

full functional dependence

Answer 9

used to refer to functional dependencies in which the entire collection of attributes in the determinant is necessary for the relationship

Question 10

composite key

Answer 10

a key that is composed of more than one attribute

Question 11

key attribute

Answer 11

an attribute that is part of a key

Question 12

superkey

Answer 12

a key that can uniquely identify any row in the able

Question 13

candidate key

Answer 13

a superkey without any unnecessary attributes. hence a minimalist key

Question 14

entity ingrity

Answer 14

the condition in which each row in the table has its own unique identity

Question 15

foreign key

Answer 15

an attribute or attributes in one table whose values must match the primary key in another table or whose values must be null

Question 16

referential integrity

Answer 16

a condition by which a dependent table’s foreign key must have either a null entry or a matching entry in the related table

Question 17

secondary key

Answer 17

an additional key, or alternate key, which can be use in addition to the primary key to locate specific data

Question 18

existence dependence

Answer 18

the entity can exist in the database only when it is associated with another related entity occurence, hence it has a mandatory foreign key

Question 19

non identifying relationship

Answer 19

aka a weak relationship. exists if the primary key of the related entity foes not contain a primary key component of the parent entity

Question 20

identifying relationship

Answer 20

a strong relationship when the primary key of the related entity contains a primary key component of the parent entity

Question 21

characteristics of a weak entity

Answer 21

• the entity is existence-dependent
• the entity has a primary key that is partially or totally derived from the parent entity in the relationship

Question 22

optional participation

Answer 22

one entity occurrence does not require a corresponding entity occurrence in a particular relationship

Question 23

cardinality

Answer 23

the minimum and maximum number of entity instances in a relation

Question 24

mandatory participation

Answer 24

one entity occurrence requires a corresponding entity occurrence in a particular relationship

Question 25

relationship degree

Answer 25

indicates the number of entities or participants associated with a relationship

Question 26

unary relationship

Answer 26

exists when an association is maintained within a single entity

Question 27

binary relationship

Answer 27

exists when two entities are associated

Question 28

ternary relationship

Answer 28

exists when three entities are associated

Question 29

recursive relationship

Answer 29

a relationship within a single entity type

Question 30

associative (composite) entities

Answer 30

• used to represent an M:N relationship
• composed of the primary key attributes of each parent entity