• Open Menu Close Menu
  • Apple
  • Shopping Bag
  • Apple
  • Mac
  • iPad
  • iPhone
  • Watch
  • TV
  • Music
  • Support
  • Search apple.com
  • Shopping Bag

Lists

Open Menu Close Menu
  • Terms and Conditions
  • Lists hosted on this site
  • Email the Postmaster
  • Tips for posting to public mailing lists
Multiple Self - joins
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Multiple Self - joins


  • Subject: Multiple Self - joins
  • From: Florijan Stamenkovic <email@hidden>
  • Date: Wed, 12 Jan 2005 20:47:36 +0100

Yes, I think I understand what you need.

To set up a to-many relationship to the same table (a self join) you need to make another entity for the linking. That entity must have two attributes defined as primary keys. They should both look the same as you primary key in the table where you want the joins. Then you set up a to many relationship from your original table to one of the keys in the second (helping entity). Then you set up a to-one relationship from the second identity to the primary key in the first identity. Then you go to your second identity and flatten the to-one relationship in it into your first entity. Effectively you will end up with a to-many relationship in the first entity but referring to the records in the same entity. You will never instantiate the second entity by hand, so you should hide it. It has to be there to provide the mechanism though.

Contact me if you i wasn't clear enough. I know this works because I just used it.

Best regards,
Florijan

_______________________________________________
Do not post admin requests to the list. They will be ignored.
Webobjects-dev mailing list      (email@hidden)
Help/Unsubscribe/Update your Subscription:
This email sent to email@hidden


  • Follow-Ups:
    • Re: Multiple Self - joins
      • From: Chuck Hill <email@hidden>
  • Prev by Date: Re: Multiple Self-joins
  • Next by Date: Re: Multiple Self-joins
  • Previous by thread: Re: Multiple Self-joins
  • Next by thread: Re: Multiple Self - joins
  • Index(es):
    • Date
    • Thread