Question

In the world of database design and building it is very important to define Primary keys in each table. The text this week talks about primary keys. What are they and why are they so important to a properly functioning database?

Answer 1

A Primary Key in an Access database table is a field with unique values for each record in the table. One can use the key to connect data between tables. Values of the key can be used to refer to entire records, because each record has a different value for the key. Each table can only have one primary key. Access can automatically create a primary key field for you when you create a table, or you can specify the fields that you want to use as the primary key. This article explains how and why to use primary keys.

Data encryption converts data from an easily read local language into a code that can be read only by those with the correct decryption key. The data are encoded during the input or transmission stage, then decrypted at output by the person authorized to receive them. Other controls designed to reduce the risk of interception and to detect errors or alterations in data transmissions include routing verification and message acknowledgement.    

Access uses primary key fields to quickly associate data from multiple tables and combine that data in a meaningful way. It is possible to include the primary key fields in other tables to refer back to the table that is the source of the primary key. In those other tables, the fields are called foreign keys. For example, a Customer ID field in the Customers table might also appear in the Orders table. In the Customers table, it is the primary key. In the Orders table it is called a foreign key. A foreign key, simply stated, is another table's primary key.