The relationship to a reference data group will always
be defined via a Foreign Key, whose values will be compared to both data groups.
The values of the Foreign Key correspond, as a rule, to the Primary Key of the
referenced data group. Select the data field, in our example the ProductID
field, in the right-hand column and with the help of the
arrow buttons, assign it as the Foreign Key, which contains the
Primary Key of the data group, to which the reference will be created.