Office 2007 Bible

Relational Databases

Microsoft Access is a relational database development system. Access data is stored in related tables, where data in one table (such as customers) is related to data in another table (such as orders). Access maintains the relationships between related tables, making it easy to extract a customer and all of the customer’s orders, without losing any data or pulling order records not owned by the customer.

Working with multiple tables

Multiple tables simplify data entry and reporting by decreasing the input of redundant data. By defining two tables for an application that uses customer information, for example, you don’t need to store the customer’s name and address every time the customer purchases an item.

After you’ve created the tables, they need to be related to each other. For example, if you have a Contacts table and a Sales table, you must relate the Contacts table to the Sales table in order to see all the sales records for a Contact. If you had only one table, you would have to repeat the Contact name and address for each sale record. Two tables let you look up information in the Contact table for each sale by using the related fields Contact ID (in Contacts) and Buyer ID (in Sales). This way, when a customer changes address, for example, the address changes only in one record in the Contact table; when the Sales information is onscreen, the correct contact address is always visible.

Separating data into multiple tables within a database makes the system ...