python笔记(数据库：ORM框架)

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

Base = declarative_base()


# 创建表单

class UserType(Base):                                   #继承base父类
    __tablename__ = 'usertype'                       #表的名字
    id = Column(Integer, primary_key=True, autoincrement=True)# 创建表行  Integer：int型    
    title = Column(VARCHAR(24), nullable=True, index=True)       #nullable：是否为空 index：是否添加索引


class User(Base):
    __tablename__ = 'user'
    id = Column(Integer, primary_key=True, autoincrement=True)
    name = Column(VARCHAR(32), nullable=True, index=True)
    email = Column(VARCHAR(32), unique=True)
    user_type_id = Column(Integer, ForeignKey('usertype.id')) #创建外键

    user_type = relationship('UserType', backref='xxoo')  # 和UserType建立关系


# 添加表
def create_db():
    engine = create_engine('mysql+pymysql://root:@127.0.0.1:3306/db2?charset=utf8', max_overflow=5)
    Base.metadata.create_all(engine)


# 删除表
# def drop_db():
#     engine = create_engine('mysql+pymysql://root:@127.0.0.1:3306/db2?charset=utf8',max_overflow=5)
#     Base.metadata.drop_all(engine)

create_db()

#建立会话
engine = create_engine('mysql+pymysql://root:@127.0.0.1:3306/db2?charset=utf8', max_overflow=5)
Session = sessionmaker(bind=engine)
session = Session()

# #添加一条数据
# obj1 = UserType(title = 'haha')
# session.add(obj1)

# #添加多条数据
# objs = [
#     UserType(title = 'haha'),
#     UserType(title = 'hehe'),
#     UserType(title = 'hihi'),
# ]
# session.add_all(objs)

# 查看数据
# user_type_list = session.query(UserType).all()
# for row in user_type_list:
#     print(row.id,row.title)
'''
#条件
#filter_by:传的是参数  filter：传的是表达式
user_type_list = session.query(UserType).filter_by(title='xixi').all()
user_type_list = session.query(UserType).filter(UserType.id>1,UserType.title=='xixi').all() #默认是and
user_type_list = session.query(UserType).filter(UserType.id.between(1,3),UserType.title=='xixi').all()
user_type_list = session.query(UserType).filter(UserType.id.in_([1,2,3])).all()
user_type_list = session.query(UserType).filter(~UserType.id.in_([1,2,3])).all()
user_type_list = session.query(UserType).filter(UserType.id.in_(session.query(UserType.id).filter_by(title=='xixi'))).all()

from sqlalchemy import and_,or_
user_type_list = session.query(UserType).filter(and_(UserType.id>1,UserType.title=='xixi')).all()
user_type_list = session.query(UserType).filter(or_(UserType.id>1,UserType.title=='xixi')).all()
user_type_list = session.query(UserType).filter(
                                            or_(
                                            UserType.id<4,
                                            and_(UserType.id>1,UserType.title=='xixi')
                                            )
                                            ).all()
#通配符
user_type_list = session.query(UserType).filter(UserType.title.like('x%')).all()
user_type_list = session.query(UserType).filter(~UserType.title.like('x%')).all()


#限制
user_type_list = session.query(UserType)[1:2]

#排序
user_type_list = session.query(UserType).filter(UserType.title.desc()).all()
user_type_list = session.query(UserType).filter(UserType.id.asc(),UserType.title.desc()).all()




#分组
from sqlalchemy.sql import func
user_type_list = session.query(UserType).group_by(UserType.title).all()
user_type_list = session.query(
                                func.max(UserType.id),
                                func.min(UserType.id),
                                func.sum(UserType.id)).group_by(UserType.title).all()

user_type_list = session.query(
                                func.max(UserType.id),
                                func.min(UserType.id),
                                func.sum(UserType.id)).group_by(UserType.title).having(func.min(UserType.id)>2).all()


#连表：
user_type_list = session.query(UserType,User)  # 相当于select * from UserType, User
user_type_list = session.query(UserType,User).filter(UserType.id == User.usertype_id)  # 相当于select * from UserType, User where UserType.id = User.usertype_id
user_type_list = session.query(UserType).join(User)  #相当于inner join
user_type_list = session.query(UserType).join(User,isouter=Ture)  #相当于left join


#组合
#上下连（去重）
q1 = session.query(UserType.title).filter(UserType.id>2)
q2 = session.query(User.name).filter(User.id<2)
ret = q1.union(q2).all()
#上下连（不去重）
q1 = session.query(UserType.title).filter(UserType.id>2)
q2 = session.query(User.name).filter(User.id<2)
ret = q1.union_all(q2).all()


#其他
(1)select * from UserType where UserType.id in ()
ret = session.query(UserType).filter(UserType.in_([1,2,3])).all()
(2)select * from (select * from tb) as B
q1 = session.query(UserType).filter(UserType.id>2).subquery()   #当成子查询
ret = session.query(q1).all()

(3)select id,(select id from xx where id=x) from xxx;
ret = session.query(UserType.id,session.query(User).filter(User.id==1).subquery()).all()

(4)select id,(select id from xx where xxx.id=xx.id) from xxx;
   1)ret = session.query(UserType.id,session.query(User).filter(User.id==UserType.id).as_scalar()).all()


#问题1（将UserType与User连表，取值）
（1）无relationship
user_list = session.query(UserType.title,User.name).join(User,isouter=Ture)
for row in user_list:
    print(row.title,row.name)
（2）有relationship
user_list = session.query(UserType)
for row in user_list:
    print(row.title,row.name)

#问题2 获取用户类型
（1）无relationship
user_list = session.query(UserType)
for row in user_list:
    print(row.title,session.query(User).filter(User.user_type_id==row.id).all())
（2）有relationship    
user_list = session.query(UserType)
for row in user_list:
    print(row.title,row.xxoo)    


'''

# user_type_list = session.query(UserType).filter(UserType.id>1)   #可以设定条件
# for row in user_type_list:
#     print(row.id,row.title)

# user_type_list = session.query(UserType.title).filter(UserType.id>1)   #可以设定查看的参数
# for row in user_type_list:
#     print(row.title)

# 删除（先查后删）
# session.query(UserType.title).filter(UserType.id>1).delete()

# 修改(第一种写法)：满足条件的会全部修改
# user_type_list = session.query(UserType.title,UserType.title).filter(UserType.id>2).update({UserType.title:'xixi'})
# 修改(第二种写法)：在原数据的基础上拼接字符
# user_type_list = session.query(UserType.id,UserType.title).filter(UserType.id>2).update({UserType.title:UserType.title+'00'},synchronize_session=False)
# 在原数据的基础上拼接数字
# user_type_list = session.query(UserType.id,UserType.title).filter(UserType.id>2).update({UserType.id:UserType.id+1},synchronize_session='evaluate')

session.commit()
session.close()