sqlalchemy的使用1--添加/查询表格的行（即实例）

from sqlalchemy import Column,String,create_engine,ForeignKey,MetaData,Table,Integer
from sqlalchemy.orm import sessionmaker,relationship
from sqlalchemy.ext.declarative import declarative_base

Base = declarative_base()

class User(Base):
__tablename__ = 'user'

id = Column(String(20), primary_key=True)
name = Column(String(20))
# 一对多:
books = relationship('Book')

class Book(Base):
__tablename__ = 'book'

id = Column(String(20), primary_key=True)
name = Column(String(20))
# “多”的一方的book表是通过外键关联到user表的:
user_id = Column(String(20), ForeignKey('user.id'))

# 初始化数据库连接:
engine = create_engine('mysql+mysqlconnector://root:password@localhost:3306/test')
# 创建DBSession类型:
DBSession = sessionmaker(bind=engine)

session = DBSession()
# 创建新User对象:
new_user = User(id='5', name='Bob')
# 添加到session:
session.add(new_user)
# 提交即保存到数据库:
session.commit()
# 关闭session:
session.close()

# 创建Session:
session = DBSession()
# 创建Query查询，filter是where条件，最后调用one()返回唯一行，如果调用all()则返回所有行:
user = session.query(User).filter(User.id=='5').one()
# 打印类型和对象的name属性:
print('type:', type(user))
print('name:', user.name)
# 关闭Session:
session.close()