OnDelete (Hibernate Javadocs)

```
@Target({METHOD,FIELD,TYPE})
@Retention(RUNTIME)
public @interface OnDelete
```
Specifies an on delete action for a foreign key constraint. The most common usage is @OnDelete(action = CASCADE). Note that this results in an on delete cascade clause in the DDL definition of the foreign key. It's completely different to CascadeType.REMOVE.
Like database triggers, on delete actions can cause state held in memory to lose synchronization with the database.

- Required Element Summary
  
  Required Elements
  Modifier and Type Required Element Description
  
  OnDeleteAction action
  The action to taken by the database when deletion of a row would cause the constraint to be violated.

- Element Detail
  - action
```
OnDeleteAction action
```
    The action to taken by the database when deletion of a row would cause the constraint to be violated.