Bill, Instead of storing the default mailbox in the user table, you could add a boolean field in the mailbox table to indicate default status. This would solve your integrity and circular reference concerns. Jeffrey -- Cheers. Jeffrey Barke jeffery.barke at theMechanism.com Lead Developer, US theMechanism - New York City 440 9th Avenue, 8th Floor New York, NY 10001-1631 t: +1 212.404.3150 c: +1 917.941.1232 f: +1 212.404.3228 http://www.theMechanism.com Subscribe to theMechcast, our monthly Podcast: http://feeds.feedburner.com/theMechcast theMechanism - London 3rd Floor 405 The Strand London E14 9FW United Kingdom t: +44 (0)20 7240 4942 f: +44 (0)20 7240 2262 -- The information contained in this Electronic mail message is attorney privileged and confidential information intended only for the use of the individual or entity named above. Such information also is intended to be privileged, confidential, and exempt from disclosure under applicable law. If the reader of this message is not the intended recipient or the employee or agent responsible to deliver it to the intended recipient, you are hereby notified that any dissemination, distribution, or copying of this communication is strictly prohibited. If you have received this communication in error, please notify us immediately by telephone. Blah, blah, blah... -- On May 18, 2007, at 2:17 AM, Bill Moseley wrote: > Say I have a mail reader application where people can create their own > mailboxes (folders). So I have a table: > > create table mailbox ( > id integer, > name text, > owner int references user(id) > ); > > So, now the user table should store their default mailbox > (ignoring that I've referenced user above before defining it) > > create table user ( > id integer, > name text, > email text, > default_mailbox integer references mailbox(id) > ); > > How can I ensure (in the database) that default_mailbox references a > mailbox that has its owner set to the same user? Obviously, don't > want one user's default mailbox to reference another user's mailbox. > > I'm not thrilled by the circular references there. > > > -- > Bill Moseley > moseley at hank.org > > -- > > * * Please support the community that supports you. * * > http://evolt.org/help_support_evolt/ > > For unsubscribe and other options, including the Tip Harvester > and archives of thelist go to: http://lists.evolt.org > Workers of the Web, evolt !