>>Hi,
>>
>>I've got a SQL Server Express 2008 R2 database which has a Person table where I store People and their dependents like this:
>>
>>PersonId
>>Name
>>ParentId
>>
>>So one PersonID can have many dependents by storing their ID in the ParentID field (simple self join).
>>
>>I want to set up referential Integrity on this table so that if a parent is deleted, their dependents are deleted (cascade). I created a database diagram, dropped my Person table on it and then dragged the PersonId field to the ParentID field. However, when I try to set the Delete Rule to Cascade, it is disabled.
>>
>>How can I do this?\
>
>I don't believe such complex RI is supported. Most likely you need to implement this RI through the trigger.

Should this do it:

CREATE TRIGGER PersonsDeleteDependents 
   ON  Persons
   FOR DELETE
AS 
BEGIN
	-- SET NOCOUNT ON added to prevent extra result sets from
	-- interfering with SELECT statements.
	SET NOCOUNT ON;

    -- Insert statements for trigger here
    delete Persons
    from Persons
    inner join deleted on deleted.personid = persons.parentid

END

?