Database Design for Mere Mortals Ch. 7 Flashcards
How do you identify and establish tables for a new database?
By using the Preliminary Table List
Why do you use the Preliminary Field List to help you define tables for the database?
To help you define tables for the database because the fields on the list may imply subjects that the database needs to track
What action do you take when an item on the list of subjects and a differently named item on the Preliminary Table List both represent the same subject?
Select the name that best represents the subject and use it as the sole identifier for that subject
What information does the Final Table List provide?
Provides the name, type, and description of each table in the database
State three guidelines for creating table names.
— Create a unique, descriptive name that is meaningful to the entire organization
— Create a name that accurately, clearly, and unambiguously identifies the subject of the table
— Use the minimum number of words necessary to convey the subject of the table
— Don’t use words that convey physical characteristics
— Don’t use acronyms and abbreviations
— Don’t use proper names or other words that will unduly restrict the data that can be entered into the table
— Don’t use a name that implicitly or explicitly identifies more than one subject
— Do use the plural form of the name
State two guidelines for composing table descriptions.
— Include a statement that accurately defines the table
— Include a statement that explains why this table is important to the organization
— Compose a description that is clear and succinct
— Do not include implementation-specific information in your table description, such as how or where the table is used
— Do not make the table description for one table dependent upon the table description of another table
— Do not use examples in a table description
How do you assign fields to a table on the Final Table List?
To a table on the Final Table List by determining which fields best represent characteristics of the table’s subject
State three guidelines for creating field names.
— Create a unique, descriptive name that is meaningful to the entire organization
— Create a name that accurately, clearly, and unambiguously identifies the characteristic a field represents
— Use the minimum number of words necessary to convey the meaning of the characteristic the field represents
— Don’t use acronyms and use abbreviations judiciously
— Don’t use words that could confuse the meaning of the field name
— Don’t use names that implicitly or explicitly identify more than one characteristic
— Use the singular form of the name
What two problems can a poorly designed field cause?
Can cause duplicate data and redundant data
What can you use to resolve field anomalies?
By ensuring that the field complies with the Elements of the Ideal Field
State three of the Elements of the Ideal Field.
— It represents a distinct characteristic of the subject of the table
— It contains only a single value
— It cannot be deconstructed into smaller components
— It does not contain a calculated or concatenated value
— It is unique within the entire database structure
— It retains a majority of its properties when it appears in more than one table
Under what condition is redundant data acceptable?
When it is the result of resolving a multivalued field or an unnecessary duplicate field, but only when you’re in the initial stages of designing tables
In general terms, what three steps do you follow to resolve a multivalued field?
- Remove the field from the table and use it as the basis for a new table.
- Use a field from the original table to relate the original table to the new table
- Assign an appropriate name, type, and description to the new table and ass it to the Final Table List
When is it necessary to use a duplicate field in a table?
When the field serves to establish a relationship between two tables
How can you refine table structures?
By ensuring that each table complies with the Elements of the Ideal Table
