SqlAlchemy Migrate Declarative

I've modified the tutorial on the SqlAlchemy-Migrate tutorial to declarative syntax for my Pylons Pyramid project. I can successfully upgrade and downgrade, but I'm concerned about the Base.metadata.drop_all(migrate_engine) command below. Here is my migration file:

from sqlalchemy import Column
from sqlalchemy.types import Integer, String, DateTime
from sqlalchemy.sql import func
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import scoped_session, sessionmaker

from zope.sqlalchemy import ZopeTransactionExtension

DBSession = scoped_session(sessionmaker(extension=ZopeTransactionExtension()))
Base = declarative_base()

class User(Base):
    __tablename__ = 'users'
    id = Column(Integer, primary_key=True)
    email = Column(String(75), unique=True)
    fullname = Column(String(60))          
    password = Column(String(51))          
    last_login = Column(DateTime)          
    date_joined = Column(DateTime, default=func.now())

def upgrade(migrate_engine):
    # Upgrade operations go here. Don't create your ow开发者_如何学Cn engine; bind migrate_engine
    # to your metadata
    Base.metadata.bind = migrate_engine
    Base.metadata.create_all(migrate_engine) # IS THIS DANGEROUS?

def downgrade(migrate_engine):
    # Operations to reverse the above upgrade go here.
    Base.metadata.bind = migrate_engine
    Base.metadata.drop_all(migrate_engine) # IS THIS DANGEROUS?

[edit] My question was how to individually create tables. I didn't know this was my question until asking the wrong question enough, to get to the correct question.

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The proper solution on upgrade is to get the table and create it individually, like such:

def upgrade(migrate_engine):
    # Upgrade operations go here. Don't create your own engine; bind migrate_engine
    # to your metadata
    User.__table__.create(migrate_engine)

and, for downgrading:

def downgrade(migrate_engine):
    # Operations to reverse the above upgrade go here.
    User.__table__.drop(migrate_engine)