Gets a list of joined child data sources (if any) of the first data source in the container.
Returns an array of data source IDs.
A joined child data source of a given data source A is a data source that have a Relate control linked to A, and has its 'Joined' property set to 'Yes'. Such data sources are typically used in grid controls of their parent data source. They show their related record data as (read-only) fields in these grids.
With the possibility of using embedded data sources (i.e. making these data sources an embedded member of their parent data sources), the usage of this feature is somewhat limited; however, if only a few fields of a joined child data source are required and the table is much smaller than the parent table, then this feature may still be somewhat faster and easier than using embedded data sources.