| # Possible values Child will be deleted All children that refer to the parent will be deleted. Note If the reference does not identify the relation this can result in the automatic deletion of many records. For example if the relation between the parent and child is not one-to-one but one-to-many. Restricted (with counter) Deletion of the parent is restricted if any child refers to the parent. A reference counter is checked, which indicates how many children refer to the parent. With each database action this counter is checked and updated, if necessary. Nullifies The field(s) of the child, which refer(s) to the parent that has been deleted, will be made empty (spaces or zero value). No check If the parent has been deleted, no check or action will be done on the child occurrences which refer to the parent. In that case the referential integrity of the database cannot be guaranteed. Lookup (Restricted) Deletion of the parent is restricted if any child refers to the parent. |