Chapter 04 - Logical Database Design

Question 1

relation

Answer 1

a two-dimensional table of data

Question 2

primary key

Answer 2

an attribute or a combination of attributes that uniquely identifies each row in a relation

Question 3

composite key

Answer 3

a primary key that consists of more than one attribute

Question 4

foreign key

Answer 4

an attribute in a relation that serves as the primary key of another relation in the same database

Question 5

null

Answer 5

A value that may be assigned to an attribute when no other value applies or when the applicable value is unknown.

Question 6

entity integrity rule

Answer 6

A rule that states that no primary key attribute (or component of an attribute) may be null

Question 7

referential integrity constraint

Answer 7

a rule that states that either each foreign key value must match a primary key value in another relation or the foreign key value must be null.

Question 8

well-structured relation

Answer 8

a relation that contains minimal redundancy and allows users to insert, modify, and delete the rows in a table without errors or inconsistencies

Question 9

anomaly

Answer 9

an error or inconsistency that may result when a user attempts to update a table that contains redundant data

Question 10

surrogate primary key

Answer 10

a serial number or other system-assigned primary key for a relation

Question 11

recursive foreign key

Answer 11

a foreign key in a relation that references the primary key values of the same relation

Question 12

normalization

Answer 12

the process of decomposing relations with anomalies to produce smaller, well-structured relations

Question 13

normal form

Answer 13

a state of a relation that requires that certain rules regarding relationships between attributes (or functional dependencies) are satisfied

Question 14

functional dependency

Answer 14

a constraint between two attributes in which the value of one attribute is determined by the value of another attribute

Question 15

determinant

Answer 15

the attribute on the left side of the arrow in a functional dependency

Question 16

candidate key

Answer 16

an attribute, or combination of attributes, that uniquely identifies a row in a relation

Question 17

first normal form (1NF)

Answer 17

a relation that has a primary key and in which there are no repeating groups

Question 18

second normal form (2NF)

Answer 18

a relation in first normal form with no partial functional dependencies

Question 19

partial functional dependency

Answer 19

a functional dependency in which one or more nonkey attributes are functionally dependent on part (but not all) of the primary key

Question 20

third normal form (3NF)

Answer 20

a functional dependency in second normal form with no transitive dependencies

Question 21

transitive dependency

Answer 21

a functional dependency between the primary key and one or more nonkey attributes that are dependent on the primary key via another nonkey attribute

Question 22

synonyms

Answer 22

two (or more) attributes that have different names but the same meaning

Question 23

alias

Answer 23

an alternative name used for an attribute

Question 24

homonym

Answer 24

an attribute that may have more than one meaning

Question 25

enterprise key

Answer 25

a primary key whose value is unique across all relations