Component Extensions

Syntax Form

[foreign_key_annotations]
EXTEND field : foreign_key_addition | value_help_addition;

Definition

Component extensions can be used:

to add/overrule value help or foreign key assignments to/of components from an include structure
in append structures to add value help or foreign key assignments to components of the original structure

A component extension is introduced with the EXTEND keyword, followed by the name of the component, and a foreign key or value help addition, or both.

Notes

If a structure is included, you can remove existing value helps or foreign keys using the REMOVE VALUE HELP or REMOVE FOREIGN KEY keywords.

Example

The zip_code and street components of the address include structure are extended:

For the zip_code component, a foreign key relationship is added.
For the street component, the value help originally defined in the included structure is removed for usage in the employee structure.

  ...
  office_address : INCLUDE address
    EXTEND zip_code: WITH FOREIGN KEY subsideries
      WHERE plz = employee.zip_code
    EXTEND street:
      REMOVE VALUE HELP;
  ...

Note To find more information about how to use component extensions in an append structure, see an example in the chapter Append Structures.