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The Data Dictionary As a Programming Resource

The Data Dictionary is the most important tool for database developers. The Data Dictionary allows developers to create a database and specify the properties that define the objects, or components, of that database. Database objects include tables, fields, indexes, and sequences. Collectively, these defining properties are called schema. Once you establish your schema, you can create procedures to create records and populate your database.

The Data Dictionary is also a vital tool for 4GL programmers. In addition to object definitions, the schema includes properties that affect the default behavior of Progress procedures as they interact with database objects. These properties are know as application defaults. For example, suppose a particular database field needs upper and lower numeric limits. To keep values within the limits, you would have to code checks into every procedure that accesses the field. Checking data to make sure it meets criteria is known as validation. Instead of coding your validation routines, you can take advantage of Progress database validation properties to automatically check the data.

The purpose of this chapter is to teach you how to use the Data Dictionary to view the schema of a Progress database and manage important application defaults. Wisely using application defaults:

To illustrate how the Data Dictionary and application defaults work, you’ll create and use your own copy of the sports database.


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