Set this to true to include extra join columns on each table.
Some tools may require an ON condition (or generate them automatically) based on foreign key references. By setting IncludeJoinColumns to true, every table will include a foreign key reference to the other tables. These columns will not return any data and are not useful for anything other than passing as ON conditions to perform joins upon.
In Azure Analysis Services, the dimensions and measures making up the tables are already related naturally. There is no context on which to join them provided. Therefore, the CData Tableau Connector for Azure Analysis Services supports joining without specifying an ON condition, so they are optional to specify.