All children that refer to the parent will be updated.
Note
If the reference does not identify the relation this may
result in the automatic update of many records. For example if the relation
between the parent and the child is not one-to-one but one-to-many.
Restricted (with counter)
Any change of the primary key fields of the parent is not
allowed if any child refers to this record. A reference counter is checked,
which indicates how many children refer to the parent. With each database
action this counter will be checked and updated, if necessary.
Nullifies
The field(s) of the child, which refer(s) to the updated parent
record, will be made empty (spaces or zero values).
No check
If the parent is changed, no check or action will be done on
the child records which refer to the parent. In that case the referential
integrity of the database cannot be guaranteed.
Lookup (Restricted)
Any change of the primary key fields of the parent is not
allowed if any child refers to this record.