It is a good idea to write down the purpose of the database on paper — its purpose, how you expect to use it, and who will use it. For a small database for a home based business, for example, you might write something simple like "The customer database keeps a list of customer information for the purpose of producing mailings and reports." If the database is more complex or is used by many people, as often occurs in a corporate setting, the purpose could easily be a paragraph or more and should include when and how each person will use the database. The idea is to have a well developed mission statement that can be referred to throughout the design process. Having such a statement helps you focus on your goals when you make decisions.

What is good database design?

Before creating database, first we must know the following things:

• Duplicate information also called redundant data is bad, because it wastes space and increases the likelihood of errors and inconsistencies.
• Accurate information is important. If your database contains incorrect information, any reports that pull information from the database will also contain incorrect information. As a result, any decisions you make that are based on those reports will then be misinformed.

• No redundant data.
• Provides Access with the information it requires to join the information in the tables together as needed.
• Helps support and ensure the accuracy and integrity of your information.
• Accommodates your data processing and reporting needs.

The design process consists of the following steps:

Determine the purpose of your database
This helps prepare you for the remaining steps.

Find and organize the information required
Gather all of the types of information you might want to record in the database, such as product name and order number.

Divide the information into tables
Divide your information items into major entities or subjects, such as Products or Orders. Each subject then becomes a table.

Turn information items into columns
Decide what information you want to store in each table. Each item becomes a field, and is displayed as a column in the table. For example, an Employees table might include fields such as Last Name and Hire Date.

Specify primary keys
Choose each table’s primary key. The primary key is a column that is used to uniquely identify each row. An example might be Product ID or Order ID.

Set up the table relationships
Look at each table and decide how the data in one table is related to the data in other tables. Add fields to tables or create new tables to clarify the relationships, as necessary.

Refine your design
Analyze your design for errors. Create the tables and add a few records of sample data. See if you can get the results you want from your tables. Make adjustments to the design, as needed.

Apply the normalization rules
Apply the data normalization rules to see if your tables are structured correctly. Make adjustments to the tables, as needed.



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