Michael, Thanks for your clarification. I understand what server_onupdate does now.
It's weird that I saw some examples like this one: https://groups.google.com/d/topic/sqlalchemy/qYpPtgNXzAg/discussion On Monday, October 1, 2012 1:52:22 PM UTC+8, Michael Bayer wrote: > > > On Sep 30, 2012, at 9:48 PM, Roy Shan wrote: > > > Hi, Michael: > > > > I am trying to use server_onupdate in schema definition, but > server_onupdate doesn't seem to work. > > > > Here's an example: > > > > from sqlalchemy import * > > engine = create_engine('mysql://root:@localhost:3306/test?charset=utf8', > echo =True) > > m = MetaData(bind=engine) > > t = Table('t', m, > > Column('a', Integer), > > Column('b', TIMESTAMP(), server_onupdate=text('current_stamp')) > > ) > > m.drop_all() > > m.create_all() > > > > the output of this script is: > > > > CREATE TABLE t ( > > a INTEGER, > > b TIMESTAMP NULL > > ) > > > > The server_onupdate has no effect. > > While it seems like it should, that's currently not what server_onupdate > does. Most databases do not support an inline form of "ON UPDATE" within > column definitions; MySQL is an exception to this but we do not support > MySQL's syntax directly right now. server_onupdate's purpose is to place > a marker on the column, so that the ORM knows that some separately defined > trigger or rule has been established that will cause the column to receive > a new value when an UPDATE statement executes. > > To render MySQL's ON UPDATE you'd need to emit a separate ALTER > instruction for now. 0.8 will offer a compile hook, but this is still not > a first class "mysql_onupdate" feature as of yet. > > > -- You received this message because you are subscribed to the Google Groups "sqlalchemy" group. To view this discussion on the web visit https://groups.google.com/d/msg/sqlalchemy/-/VHxja_Pn7nsJ. To post to this group, send email to sqlalchemy@googlegroups.com. To unsubscribe from this group, send email to sqlalchemy+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en.
