Database Design for Mere Mortals: A Hands-On Guide to Relational Database Design

State two major reasons why field specifications are important.

Field specifications are important for these reasons:

1. They help establish and enforce field-level integrity.

2. They help enhance overall data integrity.

3. They compel you to acquire a complete understanding of the nature and purpose of the data in the database.

4. They constitute the "data dictionary" of the database.

What do you gain by establishing field-level integrity ?

Field-level integrity warrants the following:

1. The identity and purpose of a field is clear, and all of the tables in which it appears are properly identified.

2. Field definitions are consistent throughout the database.

3. The values of a field are consistent and valid.

4. The types of modifications, comparisons, and operations that can be applied to the values in the field are clearly identified.

What are the three categories of elements in a field specification?

The three categories of elements within a field specification are general , physical , and logical .

Name the three types of specifications.

The three types of specifications are Unique , Generic , and Replica .

Why is it beneficial for you to compose a proper field description?

Composing a field description is extremely beneficial because it forces you (and everyone in the organization) to think carefully about the nature of the data that will be stored in the field.

What does the Data Type element indicate ?

The Data Type element indicates the nature of the data that the field stores.

What does the Character Support element indicate?

The Character Support element indicates the type of characters that a user can enter into a given field value.

What is the purpose of the Display Format element?

The Display Format element governs the appearance of a field's value when it is displayed on a screen or printed within a document.

What types of keys are indicated on a field specification?

The types of keys indicated on a field specification are non , primary , alternate , and foreign .

True or False: A null represents a blank value.

False. Null does not represent a blankit represents a missing or unknown value.

What is the significance of the Range of Values element?

The Range of Values element specifies every possible valid value for a field.

What is the purpose of an Edit Rule?

An Edit Rule designates at what point in time a user can enter a value into a field and whether he can modify that value.

What is the purpose of the Comparisons Allowed element?

The Comparisons Allowed element indicates the types of comparisons a user can apply to a given field value when he's retrieving information from the field.

What is a value expression ?

A value expression is some form of operation involving field values, literal values, or a combination of both, and it returns a single value that you can then use for a comparison operation.

When do you use a generic specification?

You use a generic specification for a field that serves as a template for other fields within the database.