python sqlalchemy 进行 mysql 数据库操作

1. 进行mysql数据库的创建，如果已经存在，就相当于进行数据库的连接操作

from sqlalchemy import create_engine
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import Column, Integer, String, Date
from sqlalchemy.orm import sessionmaker 

# 创建连接
engine = create_engine('mysql+pymysql://root:123456@localhost/oldboydb',
                       encoding='utf-8')

Base = declarative_base()  # 生成orm基类

class User(Base):
      __tablename__ = 'user'   # table的名字
    id = Column(Integer, primary_key=True)  # 创建id属性
    name = Column(String(32))  # 创建name属性
    password = Column(String(64)) # 创建密码属性

    def __repr__(self):  # 用于进行查找时的数据返回
        return '<%s name :%s>' %(self.id, self.name)

Base.metadata.create_all(engine) # 进行指令的调用，即生成table 

2. 进行数据的查询，包括条件查询和多条件查询

from sqlalchemy import create_engine
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import Column, Integer, String, Date
from sqlalchemy.orm import sessionmaker

# 创建连接
engine = create_engine('mysql+pymysql://root:123456@localhost/oldboydb',
                       encoding='utf-8')

Base = declarative_base()  # 生成orm基类

class User(Base):  # User继承了上述的操作

    __tablename__ = 'student_user'
    id = Column(Integer, primary_key=True)
    name = Column(String(32))
    password = Column(String(64))

    def __repr__(self): # 返回查询到的信息
        return '<id: %s name: %s password: %s>' %(self.id, self.name, self.password)

# 执行上述的操作
Base.metadata.create_all(engine)
Session_class = sessionmaker(bind=engine)  # 进行数据库的连接
Session = Session_class() # 生成session 实例

# 进行数据查询 .all()输出所有的检索结果，.first() 输出第一条的结果
data = Session.query(User).filter_by(name='alex').first()
print(data)
data = Session.query(User).filter(User.name == 'rain').first()
print(data)

# 多条件查询
data = Session.query(User).filter(User.name=='rain').filter(User.id > 1).first()
print(data)

3. 进行用户属性的修改

# 进行数据的条件修改
data = Session.query(User).filter(User.name=='rain').first() # 查找出数据的类
data.name = 'Tom' # 对类属性进行修改
Session.commit() # 结果的提交
print(data.id)  # 打印查找结果的id信息

4. 添加新的用户信息

fake_user = User(name='Jack', password='')  # 设置用户的名字和密码
Session.add(fake_user) # 将数据添加到表内

5. 进行用户信息的删除

data = Session.query(User).filter(User.name=='Jack').first()  # 查找用户信息
Session.delete(data)  # 删除用户
Session.commit() # 提交结果

6. 数据的回滚操作

data = Session.query(User).filter(User.name=='Jack').first() # 查找符合条件的数据
Session.delete(data) # 数据删除
Session.rollback()  # 数据回滚，取消上述操作
Session.commit() # 提交结果

7. 数据统计

print(Session.query(User).filter(User.name.in_(['alex', 'Jack'])).count())  # 统计名字是'alex'或者'Jack'的次数

# 2 

8. 根据名字进行数据分组

from sqlalchemy import func
data = Session.query(User.name, func.count(User.name)).group_by(User.name).all()
print(data)

# [('alex', 1), ('Tom', 1), ('Jack', 1)]

9. 定义数据库的student表，进行连表查询

# 定义Student类关联student table
class Student(Base):

    __tablename__ = 'student'
    id = Column(Integer, primary_key=True)
    name = Column(String(32))
    register_data = Column(Date)
    sex = Column(String(32))

    def __repr__(self):  # 返回查询到的信息
        return '<id: %s name: %s register_data: %s>' % (self.id, self.name, self.register_data)

data = Session.query(User, Student).filter(User.name==Student.name).all()

print(data)

10. 将两个表的属性进行串联, 这里将student的id属性，有上课记录study_record的stu_id 属性进行关联，构造一个学生的上课记录

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

# 创建连接
engine = create_engine('mysql+pymysql://root:123456@localhost/oldboydb',
                       encoding='utf-8')

Base = declarative_base()  # 生成orm 基类

# 构造student的类
class Student(Base):

    __tablename__ = 'student'
    id = Column(Integer, primary_key=True)
    name = Column(String(32), nullable=False)
    register_data = Column(Date, nullable=False)
    sex = Column(String(32))

    def __repr__(self):
        return '<id: %s name: %s sex: %s>'%(self.id, self.name, self.sex)

class StudyRecord(Base):

    __tablename__ = 'study_record'
    id = Column(Integer, primary_key=True)
    day = Column(Integer, nullable=False)
    status = Column(String(32), nullable=False)
    stu_id = Column(Integer, ForeignKey('student.id'))  # 构建外键

    student = relationship('Student', backref='my_study_record')

    def __repr__(self):
        return '<%s day:%s status:%s>'%(self.student.name, self.day, self.status)

Base.metadata.create_all(engine)

Session_class = sessionmaker(bind=engine)

session = Session_class()

s1 = Student(name='Alex', register_data='2015-04-21')
s2 = Student(name='Jack', register_data='2016-04-21')
s3 = Student(name='Rain', register_data='2017-04-21')
s4 = Student(name='Eric', register_data='2018-04-21')

study_obj1 = StudyRecord(day=1, status='YES', stu_id=1)
study_obj2 = StudyRecord(day=2, status='NO', stu_id=1)
study_obj3 = StudyRecord(day=3, status='YES', stu_id=1)
study_obj4 = StudyRecord(day=1, status='YES', stu_id=2)

# 进行数据的批量插入
session.add_all([s1, s2, s3, s4, study_obj1, study_obj2, study_obj3, study_obj4])

stu_obj = session.query(Student).filter(Student.name=='alex').first()
print(stu_obj.my_study_record) # 找出student='alex' 对应的学习记录

11. 一张表里的两个属性对应一张表的属性，就好比商品的收获地址和发货地址都对应的是地址数据库

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

# 创建连接
engine = create_engine('mysql+pymysql://root:123456@localhost/oldboydb',
                       encoding='utf-8')

Base = declarative_base()

class Customer(Base):

    __tablename__ = 'customer'
    id = Column(Integer, primary_key=True)
    name = Column(String(64))

    billing_address_id = Column(Integer, ForeignKey('address.id'))
    shipping_address_id = Column(Integer, ForeignKey('address.id'))

    billing_address = relationship('Address', foreign_keys = [billing_address_id])
    shipping_address = relationship('Address', foreign_keys = [shipping_address_id])

class Address(Base):

    __tablename__ = 'address'
    id = Column(Integer, primary_key=True)
    street = Column(String(64))
    city = Column(String(64))
    state = Column(String(64))

    def __repr__(self):
        return self.street

Base.metadata.create_all(engine)

Session_class = sessionmaker(bind=engine)

session = Session_class()

stu_obj = session.query(Customer).filter(Customer.name=='computer').first()
print(stu_obj.shipping_address) # 找出student='alex' 对应的学习记录

12. 构建多对多的表格类型，即一本书可以对应多个作者，一个作者可以对应多本书

orm_m2m.py

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

# 创建连接
engine = create_engine('mysql+pymysql://root:lishentao22@localhost/oldboydb?charset=utf8',
                       )

Base = declarative_base()

book_m2m_author = Table('book_m2m_author', Base.metadata,
                        Column('book_id', ForeignKey('books.id')),
                        Column('author_id', ForeignKey('authors.id')))

class Book(Base):
    __tablename__ = 'books'
    id = Column(Integer, primary_key=True)
    name = Column(String(64))
    pub_date = Column(Date)
    authors = relationship('Author', secondary=book_m2m_author, backref='books')

    def __repr__(self):
        return self.name

class Author(Base):
    __tablename__ = 'authors'
    id = Column(Integer, primary_key=True)
    name = Column(String(32))

    def __repr__(self):
        return self.name

Base.metadata.create_all(engine)

orm_m2m_api.py

from day12 import orm_m2m
from sqlalchemy.orm import sessionmaker

Session_class = sessionmaker(bind=orm_m2m.engine)
session = Session_class()

# b1 = orm_m2m.Book(name='learn python with Alex', pub_date='2014-06-02')
# b2 = orm_m2m.Book(name='learn Zhangbility with Alex', pub_date='2015-02-06')
# b3 = orm_m2m.Book(name='go alex to taiguo', pub_date='2014-02-05')
#
# a1 = orm_m2m.Author(name='Alex')
# a2 = orm_m2m.Author(name='Jack')
# a3 = orm_m2m.Author(name='Rain')
#
# b1.authors = [a1, a3]
# b3.authors = [a1, a2, a3]
#
# session.add_all([b1, b2, b3, a1, a2, a3])
# session.commit()

author_obj = session.query(orm_m2m.Author).filter(orm_m2m.Author.name=='alex').first()
# session.delete(author_obj)  # 删除这个作者

book_obj = session.query(orm_m2m.Book).filter(orm_m2m.Book.id==14).first()
book_obj.authors.remove(author_obj)

session.commit()