Database Design for Mere Mortals Ch. 9 Flashcards
State two major reasons why field specifications are important.
— Help establish and enforce field-level integrity
— Help enhance overall data integrity
— Compel you to acquire a complete understanding of the nature and purpose of the data in the database
— Constitute the ‘data dictionary’ of the database
What do you gain by establishing field-level integrity?
— The identity and purpose of a field is clear, and all the tables in which it appears are properly identified
— Field definitions are consistent throughout the database
— The values of a field are consistent and valid
— 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?
— General
— Physical
— Logical
Name three types of specifications.
— Unique
— Generic
— Replica
Why is it beneficial for you to compose a proper field description?
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 nature of the data that the field stores
What does the Character Support element indicate?
The type of characters that a user can enter into a given field value
What type of keys are indicated on a field specification?
— Non
— Primary
— Alternate
— Foreign
True or False: Null represents a blank value
False
What is the significance of the Range of Values element?
Specifies every possible valid value for a field
What is the purpose of 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
When do you use a generic specification?
For a field that serves as a template for other fields within the database
