Introduction › How Public Interfaces Differ › Optional Foreign Key Fields

Optional Foreign Key Fields

Host Public Interface tables contain many columns that are optional foreign key fields and are equal to zero when the association does not exist. Some of these columns represent unimplemented associations or mutually exclusive relationships.

In the CSE, optional foreign key fields cause a problem when the view is defined directly against the data tables, because the SQL join with the association table does not retrieve any rows when the association does not exist.

The definition of a separate view for the association to the optional foreign key lets you retrieve the correct information from the CSE.