Database Functions are a feature that some DBMS products implement to provide users with a mechanism to extend the functionality of the database server. A Database Function is a routine that accepts parameters, performs an action (such as a complex calculation) and returns the result of that action as a value. Depending on the Function, the return value can be either a single value or a result set.
Once created, a Database Function can be used as an expression in an SQL statement.
In Enterprise Architect, Database Functions can be modeled in one of two ways:
|·||As individual objects (the default method) or|
|·||As Operations in a container|
Functionally the two methods result in the same DDL being produced. The main difference is visual - by having several Operations in one container, you have fewer elements and less clutter on the diagram.
Database Functions modeled as individual objects are UML Classes with the stereotype «function»; you create these by dragging the Function icon onto a diagram from the Data Modeling Toolbox.
Operations in a Container
Database Functions modeled as operations have a container object, this being a UML Class with the stereotype «functions» (with an s on the end). Each Function is an operation with the stereotype «func». The system provides a dedicated maintenance window through which the modeler can easily manage the Functions stored as operations.