Thank you very much, I understand it from now on On 4月19日, 下午4时55分, "King Simon-NFHD78" <simon.k...@motorola.com> wrote: > > -----Original Message----- > > From: sqlalchemy@googlegroups.com > > [mailto:sqlalch...@googlegroups.com] On Behalf Of Gaicitadie > > Sent: 16 April 2010 20:06 > > To: sqlalchemy > > Subject: [sqlalchemy] Is the mapper must have a primary_key? > > > #!/usr/bin/python > > # -*- coding: UTF-8 -*- > > > from sqlalchemy import * > > from sqlalchemy.orm import * > > from sqlalchemy.ext.declarative import declarative_base > > > Base = declarative_base() > > > class Test(Base): > > __tablename__ = 'test' > > > tid = Column(Integer) > > > engine = create_engine('sqlite:///:memory:', echo=True) > > metadata = Base.metadata > > metadata.create_all(engine) > > [SNIP] > > > > > It seems must make a primary_key for table，but my table need't > > primary_key，what can i do？ > > The ORM part of SQLALchemy requires that you have some combination of columns > that uniquely identify a row in the database. This is so that when you load > an instance from the database, then modify it and flush your changes back to > the database, the updates actually get applied to the correct row. It also > means that if you load rows from the same table more than once in the same > Session, you always get the same instance back for a given row. Note that the > columns don't have to actually be a primary key in the database. > > If you are treating the database as read-only and you have rows in your table > which really are identical, you may be better off just using the lower-level > SQL expression language part of SA, which doesn't have these constraints. > > Hope that helps, > > Simon > > -- > You received this message because you are subscribed to the Google Groups > "sqlalchemy" group. > To post to this group, send email to sqlalch...@googlegroups.com. > To unsubscribe from this group, send email to > sqlalchemy+unsubscr...@googlegroups.com. > For more options, visit this group > athttp://groups.google.com/group/sqlalchemy?hl=en.- 隐藏被引用文字 - > > - 显示引用的文字 -
-- You received this message because you are subscribed to the Google Groups "sqlalchemy" group. To post to this group, send email to sqlalch...@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.
