MySQL04-SQLAchemy

MySQL04-SQLAchemy

• ORM技術:
  Object_Relational Mapping 把關係數據庫的表結構映射到對象上。

• SQLAlchemy:
  SQLalchemy 是python編程語言下的一款ORM框架，該框架建立在數據庫API之上，使用關係對象映射進行數據庫操作，簡言之便是：將對象轉換成SQL，然後使用數據API執行SQL並獲取執行結果。

from sqlalchemy import create_engine

engine = create_engine("mysql+pymysql://root:[email protected]:3306/day0613?charset=utf8", max_overflow=5)

cur =engine.execute('show databases')

res = cur.fetchall()

for row in res:
    print(row[0])

• ORM功能使用：

from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import Column, Integer, String, ForeignKey, UniqueConstraint, Index, VARCHAR
from sqlalchemy.orm import sessionmaker, relationship
from sqlalchemy import create_engine

# engine = create_engine("mysql+pymysql://root:[email protected]:3306/day0613?charset=utf8", max_overflow=5)

# cur = engine.execute(
#     "insert into users(name,email,user_type_id) values('ddddddd','dddssssss',3)"
# )



Base = declarative_base()

class User(Base):
    __tablename__ = 'usersinfo'
    id = Column(Integer,primary_key=True)
    name = Column(String(32))
    age = Column(Integer)

    __table_args__=(
        UniqueConstraint('id','name',name='uix_id_name'),
        Index('ix_id_name','id','name'),
    )


#一對多


class UserType(Base):
    __tablename__ = 'usertype'
    id = Column(Integer, primary_key=True, autoincrement=True)
    title = Column(VARCHAR(32), nullable=True, index=True)

class Users(Base):
    __tablename__ = 'users'
    id = Column(Integer, primary_key=True, autoincrement=True)
    name = Column(VARCHAR(32), nullable=True, index=True)
    email = Column(VARCHAR(16), unique=True)
    user_type_id = Column(Integer,ForeignKey("usertype.id"))

    user_type = relationship("UserType",backref='xxoo')




# 多對多

class Group(Base):
    __tablename__ = 'group'
    id = Column(Integer, primary_key=True)
    name = Column(String(64), unique=True, nullable=False)
    port = Column(Integer, default=22)


class Server(Base):
    __tablename__ = 'server'

    id = Column(Integer, primary_key=True, autoincrement=True)
    hostname = Column(String(64), unique=True, nullable=False)

class ServerToGroup(Base):
    __tablename__ = 'servertogroup'
    nid = Column(Integer, primary_key=True,autoincrement=True)
    server_id = Column(Integer, ForeignKey('server.id'))
    group_id = Column(Integer, ForeignKey('group.id'))

def init_db():
    Base.metadata.create_all(engine)
def drop_db():
    Base.metadata.drop_all(engine)



engine = create_engine("mysql+pymysql://root:[email protected]:3306/day0613?charset=utf8", max_overflow=5)

Base.metadata.create_all(engine)

session = sessionmaker(bind=engine)
session = session()



type_list =session.query(UserType)
for row in type_list:
    print(row.id,row.title,row.xxoo[0].name)

print(''.center(100,'-'))

type_list =session.query(Users)
for row in type_list:
    print(row.id,row.name,row.user_type.title)


#增

# obj1 = UserType(title='普通用戶')
# session.add(obj1)


# objs = [
#     UserType(title='超級用戶'),
#     UserType(title='白金用戶'),
#     UserType(title='黑金用戶')
# ]
# session.add_all(objs)


# 刪

# session.query(UserType.id,UserType.title).filter(UserType.id <= 2).delete()

# 改

# session.query(UserType.id,UserType.title).filter(UserType.id == 3).update({'title':'黑金黑金'})
# session.query(UserType.id,UserType.title).filter(UserType.id >2).update({UserType.title:UserType.title+'xx'},synchronize_session=False)
# session.query(UserType.id,UserType.title).filter(UserType.id > 2).update({'num':User.num+1},synchronize_session='evaluate')



session.commit()
session.close()