Self-referencing constraint in MS SQL

Question

Is it true that MS SQL restrict self-referencing constraints with ON DELETE CASCADE option? I have a table with parent-child relation, PARENT_ID column is foreign key for I

Answer 1

CREATE TRIGGER MyTable_OnDelete ON MyTable
INSTEAD OF DELETE
AS 
BEGIN

  SET NOCOUNT ON;

  DELETE FROM mt
  FROM   deleted AS D
  JOIN   MyTable AS mt
  ON     d.Id = mt.ParentId

  DELETE FROM mt
  FROM   deleted AS D
  JOIN   MyTable AS mt
  ON     d.Id = mt.Id

END

Answer 2

I just answered another question where this question was bound as duplicate. I think it's worth to place my answer here too:

This is not possible. You can solve this with an INSTEAD OF TRIGGER

create table locations 
(
    id int identity(1, 1),
    name varchar(255) not null,
    parent_id int,

    constraint pk__locations
        primary key clustered (id)

)
GO

INSERT INTO locations(name,parent_id)  VALUES
 ('world',null)
,('Europe',1)
,('Asia',1)
,('France',2)
,('Paris',4)
,('Lyon',4);
GO

--This trigger will use a recursive CTE to get all IDs following all ids you are deleting. These IDs are deleted.

CREATE TRIGGER dbo.DeleteCascadeLocations ON locations
INSTEAD OF DELETE 
AS
BEGIN
    WITH recCTE AS
    (
        SELECT id,parent_id
        FROM deleted

        UNION ALL

        SELECT nxt.id,nxt.parent_id
        FROM recCTE AS prv
        INNER JOIN locations AS nxt ON nxt.parent_id=prv.id
    )
    DELETE FROM locations WHERE id IN(SELECT id FROM recCTE);
END
GO

--Test it here, try with different IDs. You can try WHERE id IN(4,3) also...

SELECT * FROM locations;

DELETE FROM locations WHERE id=4;

SELECT * FROM locations
GO

--Clean-Up (Carefull with real data!)

if exists(select 1 from INFORMATION_SCHEMA.TABLES where TABLE_NAME='locations')
---DROP TABLE locations; 

Answer 3

It is the case that you cannot set up ON DELETE CASCADE on a table with self-referencing constraints. There is a potential of cyclical logic problems, hence it won't allow it.

There's a good article here - though it's for version 8 rather than 9 of SQL - though the same rules apply.