Here I’m with a few remarks on this issue:
What does the cardinality mean and show?
Cardinality means that values in child attributes can be null. (If they are not null, these values have to exist in parent attributes.)
At the same time, cardinality says that value of parent attribute can occur in child attribute more times.
Info on Mandatory Parent:
“0…1 to 0…n” means cardinality “zero-or-one to zero-or-more”.
If this cardinality is set, child attributes should be NULL.
If Mandatory Parent checkbox is selected, the cardinality will change to “1…1 to 0…n” and child attributes should be NOT NULL.
-> This synchronization does not work at the moment and you need to change the NULL and NOT NULL values of child attributes manually. However, it will be fixed in any future version and the synchronization between Parent Mandatory and NULL/NOT NULL value in child attributes will be automatic.
If Mandatory Parent checkbox is selected, the relationship says that the child entity is dependent on parent entity (that it is dependent on existence of the parent entity).
If Mandatory Parent checkbox is clear, the relationship says that child entity can exist even without its parent entity.
Cardinality does not determine whether foreign key constraint will be generated for right or left side. Foreign key is always created in child table (where relationship leads).
I believe this information makes this issue much clearer.
Vladka + Mario