Hi, If your database is set up to generate auto-incrementing primary keys on INSERT (such as a MySQL auto-incrementing column), then SA will retrieve the new value when the object is flushed to the database. When the object is constructed, the primary key will be None until you flush the session, at which point the row gets inserted, the new ID gets generated, read back, and appears on your instance.
(Note that depending on how the database is set up, and how you've told SQLAlchemy about the column, there may be some subtlety about the underlying operations that are performed, but that's usually invisible to the application code) The SQLAlchemy ORM tutorial is a good introduction to all this: http://www.sqlalchemy.org/docs/04/ormtutorial.html In particular, look at the end of the 'Setting up the Mapping', where it talks about the 'id' attribute being None, and the 'Saving Objects' session, where it becomes 1. Hope that helps, Simon -----Original Message----- From: sqlalchemy@googlegroups.com [mailto:[EMAIL PROTECTED] On Behalf Of jdcman Sent: 04 February 2008 03:04 To: sqlalchemy Subject: [sqlalchemy] Re: How do I Instantiate a class with an Auto-assigned Key ID Ok, so can you please tell me how I can make a class that AutoIncrements the ID automatically whenever I need to make a new record.... let me explain... As I add records, I want the ID to Auto Increment. When you say "define a constructor for your class which does not require an ID", but I REQUIRE an ID, I also require the ID to increment when I add new record. You went on to say "SQLALchemy has no constructor requirements on mapped classes", what do you mean by that? Ok, so can you give me some really simple SQLAlchemy code that would allow me to increment the ID automatically? Keep in mind, that multiple people may be adding records, so it has to sort all this out. Am I to assume that this is beyond SQLAlchemy, and no one else would ever want to do this? And this was never designed to do this? I'm a really dumb newbee here, so please be patient with me... Thanx On Feb 3, 7:38 am, "Michael Bayer" <[EMAIL PROTECTED]> wrote: > jdcman wrote: > > > our members table has an ID as theprimarykeywith an auto-assigned > >keyID. > > > When we create the class it is instantiated with the ID and also > > returns an ID. > > > obviously if we provide an ID it conflicts with the auto-generated ID. > > and if we don't provide an ID it says we didn't provide enough > > variables to instantiate the class > > so how do we define our class so that it can return an ID but doesn't > > require one to instantiate the class? > > define a constructor for your class which does not require an id....or, > don't define a constructor at all. SQLAlchemy has no constructor > requirements on mapped classes, that error is being produced by your own > application. --~--~---------~--~----~------------~-------~--~----~ 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 -~----------~----~----~----~------~----~------~--~---
