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

State two major reasons why a relationship is important.

A relationship is important for the following reasons:

1. It establishes a connection between a pair of tables that are logically related to each other.

2. It helps to refine table structures and minimize redundant data further.

3. It is the mechanism that enables you to draw data from multiple tables simultaneously .

Name the three types of relationships.

The three types of relationships are one-to-one , one-to-many , and many-to-many .

Which relationship will pose the most problems?

The many-to-many relationship will pose the most problems.

State two problems you could possibly encounter with a many-to-many relationship.

You could possibly encounter problems such as these with a many-to-many relationship:

1. It will be tedious and somewhat difficult for you to retrieve information from one of the tables.

2. One of the tables will contain a large amount of redundant data.

3. Duplicate data will exist within both tables.

4. It will be difficult to insert, update, and delete data.

What is a self-referencing relationship ?

A self-referencing relationship is a relationship that exists between the records within a given table.

How do you begin the process of identifying the relationships among the tables in the database?

You begin the process of identifying the relationships among the tables in the database by creating a matrix of all the tables.

What are the two types of questions you can ask to help you identify existing relationships?

The two types of questions you can ask to help you identify existing relationships are associative and contextual.

What shorthand symbol do you use to designate a one-to-many relationship in the table matrix ?

You use a 1:N shorthand symbol to designate a one-to-many relationship in the table matrix.

How do you determine what type of relationship officially exists between each pair of tables in the matrix?

You determine what type of relationship officially exists between each pair of tables in the matrix using formulas that correspond to the three relationship-type definitions.

How do you establish a one-to-many relationship?

You establish a one-to-many relationship by taking a copy of the primary key from the table on the "one" side of the relationship and incorporating it within the table structure on the "many" side, where it then becomes a foreign key.

True or False: Retrieving information from tables with a self-referencing relationship can be tedious and somewhat difficult.

True. Retrieving information from tables with a self-referencing relationship can be tedious and somewhat difficult.

How do you establish a self-referencing many-to-many relationship?

You establish a self-referencing many-to-many relationship as you would a dual-table many-to-many relationshipwith a linking table.

How do you refine the foreign keys in the database?

You refine the foreign keys in the database by ensuring that each one complies with the Elements of a Foreign Key.

What two element categories must you modify for a foreign key's field specification?

The two element categories you must modify for a foreign key's field specification are the General Elements and Logical Elements categories.

What is the function of a deletion rule ?

A deletion rule determines what your RDBMS should do when you place a request to delete a given record in the parent table of the relationship.

What two types of participation can you designate for a table?

The two types of participation you can designate for a table are Mandatory and Optional.

What does the degree of participation indicate ?

The degree of participation indicates the minimum number of records that a given table must have associated with a single record in the related table and the maximum number of records that the table is allowed to have associated with a single record in the related table.

When does a relationship attain relationship-level integrity ?

A relationship attains relationship-level integrity after you've verified that it is properly established and its characteristics are suitably set.