by V. McDaniel

Created on: May 03, 2008

DATABASE

For those who are not in the computer field, let's review the basics. What is a database? It is simply a method of storing information for later retrieval. It can be in the form of data in tables on a computer, but it can also be stored as information in, say, a spreadsheet. The rows and columns of the spreadsheet can uniquely identify information that you want kept about sales or customers within a company. Simple is simple, but no less a database than if it were stored in a "true" database such as as an Oracle or SQL Server database. These databases are specially written software systems for storage and retrieval of "relational" information.

RELATIONAL DATA

What is relational data? Well, it is data that can be related in some way, such as "A relates to B". Being more specific, "A relates to B" can mean "for each customer in New York, he/she belongs to exactly one area code". So to model such a relationship, we could have customer information in a table which would include name, address, area code, 7-digit phone number, etc. We could also have another table with area codes and prefixes and other such information. Our relationship, though, would insure that for each New York customer, they would have exactly on area code in which their phone prefix belongs. So we could say that there is a "one-to-many relationship" between a single customer and their area code(where they live - this gets complicated when we talk about a second number such as cell phone and the fact that a customer can have a cell phone with a non-New York area code!) We can also say that for all such New York customers, that an area code has many phone numbers. So, there is a "many-to-many relationship" between New York customers and New York phone numbers. We can simplify this many-to-many relationship by saying that for each New York customer, that each can have many phone numbers. We can also say that two customers can have the SAME phone number, if they live at the same address or share the same phone number. We can say, though, that for each customer name/address/customer phone number combination, that only one record exists. So, we have "uniquely identified" the customer. This process in its basic sense isss is what is known as "normalization", and is another basic concept of relational databases.

These concepts are but a small subset of the total in understanding relational databases, but this is good start. A Google search with the keywords "relational database basics" will take you to whatever level you want to go in learning more about relational databases.

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