The Logon table contains two fields, Password and UserName, that also could reside in the Person table. These fields are attributes of a person. They are in a separate table to keep their content secure at all times. Persons who have a legitimate need to access Eval table data for report writing and so forth do not need to see logon information. Placing logon information in its own table protects confidential information.
One alternative to using two tables is to create a SQL Server view on the Person table that excludes logon information, and allow users to access only the view; however, because the content of the Logon table is off-limits to auditors, evaluators, and individuals at all times, the design team decided to keep this data in a separate table. Defining Eval Views describes how the PT application uses views.
This table has a foreign key relationship with the Person table. This relationship is different from the other relationships in the Eval database because it is a one-to-one relationship. A record in the Person table can have only one associated record in the Logon table. The following illustration shows the column properties of the Logon table.