Flat-File Design

This type of design (sometimes known as the "throw-everything-into-one-big-table" design) has been in existence for many years and is common in databases that have been designed for implementation in nonrelational database-management systems. A flat-file design is fraught with problems, as you can see by examining the structure in Figure 14.1.

This diagram represents the structure of a single table. (Imagine how other tables within the database are structured!) You can readily see that this structure will inevitably cause problems with redundant data and inconsistent data and that it suffers from a lack of data integrity. As you've probably already noted, there are a few other problems with this structure:

• Multipart fields. SALES REP NAME includes the sales rep's first and last name, CUSTOMER NAME includes the customer's first and last name, and CUSTOMER ADDRESS includes the customer's street address, city, state, and zip code.

• Calculated fields. The ORDER AMOUNT field contains a value that is most likely manually calculated, especially if the customer is ordering more than three items. The ITEM # EXTENSION fields are all likely to be manually calculated as well. The value for a given ITEM # EXTENSION field is the result of multiplying the value of a related QUANTITY # field by the value of a related PRICE # field. (For example: ITEM 3 EXTENSION = QUANTITY 3 x PRICE 3)

• Unnecessary duplicate fields. Each of the fields pertaining to a particular item is a duplicate. For example, the ITEM 1, ITEM 2, and ITEM 3 fields are unnecessary duplicate fields.

• No true primary key. There is no field or group of fields that can uniquely identify a single record in this table. The ORDER NUMBER field is not a primary key in this table; if a customer orders more than three items, you'll have to enter another record into the table using the same order number.

• The table represents more than one subject. This table represents three subjects: customers, orders, and items. (Depending on your point of view, it also represents sales reps.)

Now that you know the elements of good database design, you're sure to avoid a design such as this.

Top Part I: Relational Database Design Chapter 1. The Relational Database Topics Covered in This Chapter Types of Databases Early Database Models The Relational Database Model Relational Database Management Systems Beyond the Relational Model What the Future Holds Summary Review Questions Chapter 2. Design Objectives Topics Covered in This Chapter Why Should You Be Concerned with Database Design? The Importance of Theory The Advantage of Learning a Good Design Methodology Objectives of Good Design Benefits of Good Design Database-Design Methods Summary Review Questions Chapter 3. Terminology Topics Covered in This Chapter Why This Terminology Is Important Value-Related Terms Structure-Related Terms Relationship-Related Terms Integrity-Related Terms Summary Review Questions Part II: The Design Process Chapter 4. Conceptual Overview Topics Covered in This Chapter The Importance of Completing the Design Process Defining a Mission Statement and Mission Objectives Analyzing the Current Database Creating the Data Structures Determining and Establishing Table Relationships Determining and Defining Business Rules Determining and Defining Views Reviewing Data Integrity Summary Review Questions Chapter 5. Starting the Process Topics Covered in This Chapter Conducting Interviews The Case Study: Mike's Bikes Defining the Mission Statement Defining the Mission Objectives Summary Review Questions Chapter 6. Analyzing the Current Database Topics Covered in This Chapter Getting to Know the Current Database Conducting the Analysis Looking at How Data Is Collected Looking at How Information Is Presented Conducting Interviews Interviewing Users Interviewing Management Compiling a Complete List of Fields Summary Review Questions Chapter 7. Establishing Table Structures Topics Covered in This Chapter Defining the Preliminary Table List Defining the Final Table List Associating Fields with Each Table Refining the Fields Refining the Table Structures Summary Review Questions Chapter 8. Keys Topics Covered in This Chapter Why Keys Are Important Establishing Keys for Each Table Table-Level Integrity Reviewing the Initial Table Structures Summary Review Questions Chapter 9. Field Specifications Topics Covered in This Chapter Why Field Specifications Are Important Field-Level Integrity Anatomy of a Field Specification Using Unique, Generic, and Replica Field Specifications Defining Field Specifications for Each Field in the Database Summary Review Questions Chapter 10. Table Relationships Topics Covered in This Chapter Why Relationships Are Important Types of Relationships Identifying Existing Relationships Establishing Each Relationship Refining All Foreign Keys Establishing Relationship Characteristics Relationship-Level Integrity Summary Review Questions Chapter 11. Business Rules Topics Covered in This Chapter What Are Business Rules? Categories of Business Rules Defining and Establishing Business Rules Validation Tables Reviewing the Business Rule Specifications Sheets Summary Review Questions Chapter 12. Views Topics Covered in This Chapter What Are Views? Anatomy of a View Determining and Defining Views Summary Review Questions Chapter 13. Reviewing Data Integrity Topics Covered in This Chapter Why You Should Review Data Integrity Reviewing and Refining Data Integrity Assembling the Database Documentation Done at Last! Summary Part III: Other Database-Design Issues Chapter 14. Bad Design-What Not to Do Topics Covered in This Chapter Flat-File Design Spreadsheet Design Database Design Based on the Database Software A Final Thought Summary Chapter 15. Bending or Breaking the Rules Topics Covered in This Chapter When May You Bend or Break the Rules? Documenting Your Actions Summary In Closing Part IV: Appendixes Appendix A. Answers to Review Questions Chapter 1 Chapter 2 Chapter 3 Chapter 4 Chapter 5 Chapter 6 Chapter 7 Chapter 8 Chapter 9 Chapter 10 Chapter 11 Chapter 12 Appendix B. Diagram of the Database-Design Process Appendix C. Design Guidelines Defining and Establishing Field Specific Business Rules Defining and Establishing Relationship Specific Business Rules Elements of a Candidate Key Elements of a Foreign Key Elements of a Primary Key Elements of the Ideal Field Elements of the Ideal Table Field-Level Integrity Guidelines for Composing a Field Description Guidelines for Composing a Table Description Guidelines for Creating Field Names Guidelines for Creating Table Names Identifying Relationships Identifying View Requirements Interview Guidelines Mission Statements Mission Objectives Relationship-Level Integrity Resolving a Multivalued Field Table-Level Integrity Appendix D. Documentation Forms Appendix E. Database-Design Diagram Symbols Appendix F. Sample Designs Appendix G. Recommended Reading Remember the name: eTutorials.org Copyright eTutorials.org 2008-2023. All rights reserved.