PG and Oracle allow you to defer foreign key constraints (Oracle apparently lets you defer *all* constraints, mmm), and MySQL and SQLite (of course) don't. I'm not sure about other databases. The SQL keyword in question is DEFERRABLE.
References: http://www.postgresql.org/docs/8.2/interactive/sql-createtable.html http://www.postgresql.org/docs/8.2/interactive/sql-set-constraints.html http://download-east.oracle.com/docs/cd/B19306_01/server.102/b14231/general.htm#i1006803 http://download-east.oracle.com/docs/cd/B19306_01/server.102/b14200/clauses002.htm#sthref2933 http://download-east.oracle.com/docs/cd/B19306_01/server.102/b14200/statements_10003.htm#i2066960 On Feb 22, 3:20 pm, Michael Bayer <[EMAIL PROTECTED]> wrote: > ive heard of foreign key constraints that dont take effect until the > tranasction actually commits, but I have never actually seen this in > practice. which databases support this feature ? i didnt think it > was so common (though not surprised PG supports it). > > On Feb 22, 2007, at 1:15 PM, Luke Stebbing wrote: > > > > > Are there any plans to handle circular dependencies by using > > deferrable foreign key constraints when available? > > > In my case, I had made the foreign key constraints deferred, but > > SQLAlchemy didn't pick up on that when I reflected the database > > metadata. I eliminated the circular dependency by using > > post_update=True, but that meant dropping a NOT NULL constraint since > > postgres can't defer those (sigh). --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "sqlalchemy" group. To post to this group, send email to sqlalchemy@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en -~----------~----~----~----~------~----~------~--~---
