Section 4

Question 1

An entity-relationship model

Answer 1

Is a high-level representation of data requirements, ignoring implementation details

Question 2

An entity

Answer 2

is a person, place, product, concept, or activity

Question 3

A relationship

Answer 3

Is a statement about two entitities

Question 4

An attribute

Answer 4

is a descriptive property of an entity

Question 5

A reflexive relationship

Answer 5

Relates an entity to itself

Question 6

An entity-relationship diagram

Answer 6

Commonly called an ER diagram, is a schematic picture of entities, relationships, and attributes.

Question 7

In entity-relationship modeling, a type is a set:

Answer 7

-An entity type is a set of things
-A relationship type is a set of related things
-An attribute type is a set of values

Question 8

an instance is an element of a set

Answer 8

-An entity instance is an individual thing
-A relationship instance is a statement about entity instances
-An attribute instance is an individual value

Question 9

Complex databases are developed in three phases:

Answer 9

Analysis
Logical Design
Physical Design

Question 10

Analysis

Answer 10

Develops an entity-relationship model, capturing data requirements while ignoring implementation details

Question 11

Logical design

Answer 11

Converts the entity-relationship model into tables, columns, and keys for a particular database system

Question 12

Physical design

Answer 12

Adds indexes and specifies how tables are organized on storage media

Question 13

Analysis steps

Answer 13

1. Discover entities, relationships, and attributes
2. Determine Cardinality
3. Distinguish strong and weak entities
4. Create supertype and subtype entities

Question 14

Logical design steps

Answer 14

1. Implement entities
2. Implement relationships
3. Implement attributes
4. Apply normal form

Question 15

Cardinality

Answer 15

Refers to maxima and minima of relationships and attributes

Question 16

Relationship maximum

Answer 16

Is the greatest number of instances of one entity that can relate to a single instance of another entity

Question 17

Relationship minimum

Answer 17

Is the least number of instances of one entity that can relate to a single instance of another entity

Question 18

A subtype entity, Supertype entity

Answer 18

A —— is a subset of another entity type, called the —–

Question 19

A partition

Answer 19

A —- of a supertype entity is a group of mutually exclusive subtype entities

Question 20

Logical design follows analysis

Answer 20

Logical design converts an entity-relationship model to tables, columns, and keys for a specific database system.

Question 21

Crow’s foot notation

Answer 21

Depicts cardinality as a circle (zero), a short line (one), or three short lines (many).

Question 22

An intangible entity

Answer 22

Is documented in the data model, but not tracked with data in the database

Question 23

What should primary keys be?

Answer 23

Simple. —– values should be easy to type and store. Small values are easy to specify in a SQL clause and speed up query processing.

Question 24

An artificial key

Answer 24

Is a single-column primary key created by the database designer when no suitable single-column or composite primary key exists. Usually, —– values are integers, generated automatically by the database as new rows are inserted to the table.
They are stable, simple, and meaningless.

Question 25

What is the dependence of one column on another called?

Answer 25

Functional Dependence

Question 26

Redundancy

Answer 26

Is the repetition of related values in a table

Question 27

Natural forms

Answer 27

Are rules for designing tables with less redundancy

Question 28

Normalization

Answer 28

Eliminates redundancy by decomposing a table into two or more tables

Question 29

What is ideal for tables with frequent inserts, updates and deletes?

Answer 29

Boyce-Codd normal form

Question 30

Denormalization

Answer 30

Means intentionally introducing redundancy by merging tables