Chapter 12 | Database Design for Mere Mortals: A Hands-On Guide to Relational Database Design

1:	Why can you refer to a view as a virtual table ?
A1:	You can refer to a view as a virtual table because it draws data from base tables rather than storing data on its own.
2:	State two reasons why views are valuable .
A2:	Views are valuable for the following reasons: You can use them to work with data from multiple tables simultaneously . They reflect the most current information. You can customize them to the specific needs of an individual or group of individuals. You can use them to help enforce data integrity. You can use them for security or confidentiality purposes.
3:	Name the types of views you can define as you design the logical structure of the database.
A3:	The types of views you can define as you design the logical structure of the database are data , aggregate , and validation .
4:	What does your RDMBS do each time you access a data view (or any type of view, for that matter)?
A4:	Each time you access a view, your RDBMS will rebuild and repopulate it using the most current data from the view's base tables.
5:	What determines the type of modifications you can make to a view's data?
A5:	Field specifications and business rules will determine what types of modifications you can make to a view's data.
6:	What is the only requirement you must fulfill in order to define a multitable data view ?
A6:	The only requirement you must fulfill in order to define a multitable data view is that the tables you use to create the view must bear a relationship to each other.
7:	Why doesn't a data view contain its own primary key?
A7:	A data view does not contain its own primary key because it is not a table; a true table stores data and requires a primary key to serve as a unique identifier for each of its records.
8:	What is the purpose of an aggregate view ?
A8:	The purpose of an aggregate view is to display information produced by aggregating a particular set of data in a specific manner.
9:	What are the most common aggregate functions that you can apply to a set of data?
A9:	Sum , Average (arithmetic mean), Minimum , Maximum , and Count are the most common aggregate functions that you can apply to a set of data.
10:	What is a grouping field ?
A10:	A grouping field is a data field within an aggregate view that "groups" multiple instances of a given value into a single instance of the value.
11:	True or False: You can modify the data in an aggregate view.
A11:	False. You cannot modify the data in an aggregate view because it is composed entirely of grouping fields and calculated fields.
12:	What is the difference between a validation table and a validation view ?
A12:	The difference between a validation table and a validation view lies in their constructiona validation table stores its own data, whereas a validation view draws data from its base tables.
13:	Name two points you would consider when identifying view requirements.
A13:	You would keep the following points in mind as you identify view requirements: Review your notes with the group. Review the data-entry , report, and presentation samples you gathered during the early stages of the design process. Examine the tables and the subjects they represent. Analyze the table relationships. Study the business rules.
14:	When should you use calculated fields ?
A14:	You should use calculated fields when they will provide pertinent and meaningful information or when they will enhance the manner in which the view uses its data.
15:	How do you define a view that displays only science- fiction books?
A15:	You define a view that displays only science-fiction books by applying a filter to the appropriate field within the view.
16:	Why must you complete a View Specifications sheet for every view in the database?
A16:	You must complete a View Specifications sheet for every view in the database because it is on this sheet that you will record the characteristics of the view.

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