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one-to-one association - how to set NULL on delete?

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sven

Post subject: one-to-one association - how to set NULL on delete?

Posted: Thu Dec 04, 2003 12:53 pm

Expert

Joined: Thu Dec 04, 2003 12:36 pm
Posts: 275
Location: Bielefeld, Germany

Let's say I have two tables:

Code:

CREATE TABLE A (
  id varchar(255) NOT NULL default '',
  bone bigint(20),
  btwo bigint(20),
  PRIMARY KEY  (id),
  UNIQUE bone_unique (bone),
  UNIQUE btwo_unique (btwo),
  KEY bone_index (bone),
  KEY btwo_index (btwo),
  FOREIGN KEY (`bone`) REFERENCES `B` (`id`),
  FOREIGN KEY (`btwo`) REFERENCES `B` (`id`)
) TYPE=InnoDB;

CREATE TABLE B (
  id bigint(20) NOT NULL auto_increment',
  PRIMARY KEY  (id),
) TYPE=InnoDB;

I'd like to have the value "bone" resp. "btwo" set to "NULL" when deleting the corresponding entity of B.
How is this possible?

I'll appreciate any help.
Thanks a lot!

Sven

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david

Post subject:

Posted: Fri Dec 05, 2003 2:38 am

Hibernate Team

Joined: Tue Aug 26, 2003 7:19 pm
Posts: 2364
Location: Brisbane, Australia

You pass in a null into the class property, eg,
A.setBone(null);

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sven

Post subject:

Posted: Fri Dec 05, 2003 6:22 am

Expert

Joined: Thu Dec 04, 2003 12:36 pm
Posts: 275
Location: Bielefeld, Germany

Thanks for your reply!

Is there no chance to let Hibernate set the column of table A to "NULL" when the corresponding record of table B is deleted?

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david

Post subject:

Posted: Fri Dec 05, 2003 10:24 am

Hibernate Team

Joined: Tue Aug 26, 2003 7:19 pm
Posts: 2364
Location: Brisbane, Australia

You have two issues.
1) The domain model and
2) The database.

You kill the association by removing it by setting the property to null. You are then free to delete the object (as it exists but is not involved in a relationship). Hibernate will not clear the store as apart of garbage collection process. I tend to think of the domain model first and then (if necessary) the database.

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jasonab

Post subject:

Posted: Wed Dec 06, 2006 7:11 pm

Beginner

Joined: Fri May 06, 2005 2:37 pm
Posts: 39

Sorry to resurrect an old thread, but I have a similar situation with a non-nullable one-to-one.

Hibernate 3.2.1

When I try to delete the entity and set the relationship to be null on the other object, hibernate will try and update the key on the object to be deleted, and the database throws a constraint error. Is there a correct way to do this?

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