There are many different types of routines. Routines can
be grouped in different ways, but are primarily grouped by their system
or user definitions, by their functionality, and by their implementation.
The following diagram illustrates the classification hierarchy
of routines. All routines can be either built-in or user-defined.
The functional types of routines are in dark grey/blue boxes and
the supported routine implementations are in light grey/orange boxes.
Built-in routine implementations are emphasized, because this type
of implementation is unique. Figure 1. Classifications
of routines
The various types of routines provide extensive support for extending
SQL language functionality and for developing more modular database
applications.
