Mod4-Relational Database

Question 1

Tables (relations), rows, columns

Answer 1

data structure

Question 2

◦ Mechanisms for implementing business rules that
maintain integrity of manipulated data

Answer 2

data integrity

Question 3

Powerful SQL operations for retrieving and modifying data

Answer 3

data manipulation

Question 4

is a named, two-dimensional table of data.

Answer 4

relation

Question 5

consists of rows (records) and columns (attribute or field).

Answer 5

table/relation

Question 6

➢ Every attribute value must be atomic (not multivalued, not composite).

Answer 6

true

Question 7

➢ Every row must be unique (can’t have two rows with exactly the same values
for all their fields).

Answer 7

true

Question 8

➢ Attributes (columns) in tables must have unique names.
➢ The order of the columns must be irrelevant.
➢ The order of the rows must be irrelevant.

Answer 8

true

Question 9

correspond with entity types and with many-to-many
relationship types.

Answer 9

relation(tables)

Question 10

correspond with entity instances and with many-to-many relationship
instances.

Answer 10

rows

Question 11

correspond with attributes.

Answer 11

columns

Question 12

The word relation (in relational database) is NOT the same as the
word relationship(in E-R model).

Answer 12

true

Question 13

are unique identifiers of the relation. Examples include employee
numbers, social security numbers, etc. This guarantees that all rows are unique.

Answer 13

primary keys

Question 14

are identifiers that enable a dependent relation (on the many side of a
relationship) to refer to its parent relation (on the one side of the relationship).

Answer 14

foreign keys

Question 15

can be simple (a single field) or composite
(more than one field).

Answer 15

keys

Question 16

usually are used as indexes to speed up the
response to user queries.

Answer 16

keys

Question 17

domain constraints
entity integrity

Answer 17

integrity constraints

Question 18

▪ Allowable values for an attribute

Answer 18

domain contraints

Question 19

No primary key attribute may be null. All primary key fields MUST have data.

Answer 19

entity integrity

Question 20

rule states that any foreign key value (on the relation of the many
side) MUST match a primary key value in the relation of the one side. (Or the foreign
key can be null)
are drawn via arrow from dependent to parent table
are implemented with foreign key to primary key references

Answer 20

referential integrity

Question 21

: E-R attributes map
directly onto the relation
Mapping Regular Entities to Relations

Answer 21

simple attributes

Question 22

Use only their
simple, component attributes
Mapping Regular Entities to Relations

Answer 22

composite attributes

Question 23

Becomes a separate
relation with a foreign key taken from the
superior entity
Mapping Regular Entities to Relations

Answer 23

multivalued attributes

Question 24

▪Becomes a separate relation with a foreign
key taken from the superior entity
▪Primary key composed of:
✓Partial identifier of weak entity
✓Primary key of identifying relation (strong
entity)

Answer 24

mapping weak entities

Question 25

➢ One-to-Many–Primary key on the one side becomes a foreign key on the many side ➢ Many-to-Many–Create a new relation with the primary keys of the two entities as its primary key ➢ One-to-One–Primary key on mandatory side becomes a foreign key on optional side

Answer 25

mapping binary relationships

Question 26

▪ Identifier Not Assigned ▪ Default primary key for the association relation is composed of the primary keys of the two entities (as in M:N relationship) ▪ Identifier Assigned ▪ It is natural and familiar to end-users ▪Default identifier may not be unique

Answer 26

mapping associative entities

Question 27

▪One-to-Many–Recursive foreign key in the same relation ▪Many-to-Many–Two relations: ▪ One for the entity type ▪ One for an associative relation in which the primary key has two attributes, both taken from the primary key of the entity

Answer 27

mapping unary relationships

Question 28

➢ One relation for each entity and one for the associative entity ➢ Associative entity has foreign keys to each entity in the relationship

Answer 28

mapping ternary(and n-ary) relationships

Question 29

➢ One relation for supertype and for each subtype ➢ Supertype attributes (including identifier and subtype discriminator) go into supertype relation ➢ Subtype attributes go into each subtype; primary key of supertype relation also becomes primary key of subtype relation ➢ 1:1 relationship established between supertype and each subtype, with supertype as primary table

Answer 29

mapping supertype/subtype relationships