Chapter 4-Database Design Methodology

Question 1

Insertion anomaly

Answer 1

A circumstance in which data may not be entered into a relation because a complete primary key is not available.

Question 2

Deletion anomaly

Answer 2

A circumstance in which unwanted data is deleted from my relation.

Question 3

Update anomaly

Answer 3

A circumstance in which redundant data in a relation may not be properly updated.

Question 4

Name the six conceptual design phases.

Answer 4

1. Identifying entities.
2. Identifying attributes and attribute domains for entities.
3. Identifying relationships.
4. Identifying candidate and primary keys for entities.
5. Creating an entity relationship diagram.
6. Reviewing the ER model by the design user and design team.

Question 5

Each entity must have what to distinguish it from other entities?

Answer 5

A unique identifier

Question 6

Once each entity has been identified and given a unique identifier what needs to happen next?

Answer 6

The attributes or characteristics of each entity must be identified.

Question 7

What needs to happen with the primary key during the identifying candidate and primary keys for entities phase?

Answer 7

The step involves determining which attribute with an entity will be used as the primary key.

Question 8

What are the four guidelines to use when determining a primary key?

Answer 8

1. The candidate key least likely to have its value changed.
2. The candidate key least likely to lose its uniqueness.
3. The candidate key that contains the fewest characters.
4. The candidate key that is easiest for the user to use.

Question 9

What is another style of database modeling?

Answer 9

Information engineering (IE)

Question 10

In an ER model what shape is used to represent entities?

Answer 10

Rectangle

Question 11

In an ER model what shape is used to represent attributes?

Answer 11

Oval

Question 12

In an ER model what indicates the primary key?

Answer 12

*

Question 13

In the IE model the attributes are placed within what?

Answer 13

A rectangle

Question 14

SMALLINT

Answer 14

16 bit signed integer

Question 15

INTEGER

Answer 15

32 bit signed integer

Question 16

DECIMAL(p,q)

Answer 16

Signed decimal number, p is digits and q is decimals.

Question 17

FLOAT(p)

Answer 17

Floating-point number of p bits Percision

Question 18

CHAR(n)

Answer 18

Fixed length string of n characters

Question 19

VARCHAR(n)

Answer 19

Variable length string of up to n characters

Question 20

DATE

Answer 20

Date in the form YYYYMMMDD

Question 21

TIME

Answer 21

Time in the form HH MM SS

Question 22

TIMESTAMP

Answer 22

Combines a DATE and a TIME

Question 23

Recursive relationship

Answer 23

An entity relationship in which an entity is involved in a relationship with itself.

Question 24

CREATE TABLE

Answer 24

Tables created with CREATE TABLE statement are based tables.

Question 25

Methodology

Answer 25

An organized documented set of procedures and guidelines for those who work in a discipline or participate in an inquiry.