Situation 3: association to root table using foreign key.

Relationship between root and non-root tables - situation 3:

Compared to the previous situation, the relationship direction has changed again: the non-root table refers to the root table.

As shown in the picture, this situation has two variants: the non-root table identifier is either hidden or used as an attribute in the BID. In the first case, the value must be generated. In either case, the implementation (including hooks) must make sure that a one-to-one aggregation relationship is maintained: each order must be in only one task.