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Normalization and Normal Forms Some of the most difficult decisions that you face as a developer are what tables to create and what fields to place in each table, as well as how to relate the tables that you create. Normalization is the process of applying a series of rules to ensure that your database achieves optimal structure. Normal forms are a progression of these rules. Each successive normal form achieves a better database design than the previous form did. Although there are several levels of normal forms, it is generally sufficient to apply only the first three levels of normal forms. The following sections describe the first three levels of normal forms.

First Normal Form To achieve first normal form, all columns in a table must be atomic. This means, for example, that you cannot store first names and last names in the same field. The reason for this rule is that data becomes very difficult to manipulate and retrieve if multiple groups are stored in a single field. Using the full name as an example, it would become impossible to sort by first name or last name independently if both groups were stored in the same field. Furthermore, you or the user must perform extra work to extract just the first name or the last name from the field.

Second Normal Form To achieve second normal form, all non-key columns must be fully dependent on the primary key. In other words, each table must store data about only one subject. To achieve second normal form, you must break this data into two tables: an order table and an order detail table. The process of breaking the data into two tables is called decomposition. It is considered to be non-loss decomposition because no data is lost during the decomposition process. After you separate the data into two tables, you can easily bring the data back together by joining the two tables in a query.

Third Normal Form To attain third normal form, a table must meet all the requirements for first and second normal form, and all non-key columns must be mutually independent. This means that you must eliminate any calculations, and you must break out data into lookup tables.

An example of a calculation stored in a table is the product of price multiplied by quantity. Instead of storing the result of this calculation in the table, you would generate the calculation in a query, or in the control source of a control on a form or a report.

This material orginally appeared in Alison Balter's book Mastering Microsoft Office Access 2007 Development. Reprinted here by author's permission.

When you need a Microsoft Access programmer for your Seattle WA business, phone call MS Access Solutions at (323) 285-0939. We have over 25 years experience in Microsoft Access programmer solutions. We create Access database applications for all sectors, consisting of hospitals, government companies, the U.S. military, universities, agriculture, workers services, and insurance provider. We can take care of the most advanced as well as complicated Access and also SQL Server database programming for your business as well as smaller projects, like fixing damaged Access database forms, MS Access reports, Access macros, and VBA code.

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