SQLALchemy 快速使用

SQLALchemy

详细的使用文档：https://www.osgeo.cn/sqlalchemy/orm/session_basics.html#update-and-delete-with-arbitrary-where-clause

1. sqlalchemy安装

pip install sqlalchemy

mysqldb是Python支持的MySQL数据库驱动

· pip install mysqlclient（Windows)
· pip install mysql-python（mix os)
· apt-get install python-mysqldb（Linux Ubuntu)

提示：ModuleNotFoundError: No module named 'MySQLdb' 安装以上

2. 数据库配置信息

'数据库类型+数据库驱动名称://用户名:密码@服务器地址:端口号/数据库名'

如：

mysql+mysqldb: //root:@localhost:3306/Students?charset=utf8

3. 核心类介绍

from sqlalchemy import Column, ForeignKey, Integer, String  # ORM中对象映射中与数据库中对应的数据类型
from sqlalchemy.ext.declarative import declarative_base     # 所有定义的类 需要基础的基类
from sqlalchemy.orm import relationship   # 表与表之间的关系定义
from sqlalchemy import create_engine   # 创建数据库之间的链接
from sqlalchemy.orm import sessionmaker  # 操作数据库之间的会话

对于数据类型可以在 # sqlalchemy/__init__.py 去查看

from .types import BLOB
from .types import Boolean
from .types import CHAR
from .types import CLOB
from .types import Date
from .types import DateTime
from .types import DECIMAL
from .types import Float
from .types import INTEGER
from .types import JSON
from .types import LargeBinary
from .types import NCHAR
from .types import Numeric
from .types import NVARCHAR
from .types import REAL
from .types import SMALLINT
from .types import SmallInteger
from .types import String
from .types import TEXT

远远不止这些，并且 提供了多种命名方式

4. 基本建表流程

# coding = utf-8

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

mysql_sql = "mysql+mysqldb://root:root@localhost:3306/blog?charset=utf8"

# 这里建立一个Person table

engine = create_engine(mysql_sql)
Base = declarative_base()


class Person(Base):
    __tablename__ = 'Person'
    id = Column(Integer, primary_key=True)
    name = Column(String(25), nullable=False)


# 创建库
Base.metadata.create_all(engine)

一对多关系

5. 一对多关系

class User(Base):
    __tablename__ = "User"
    id = Column(Integer, primary_key=True)
    username = Column(String(64), nullable=False, index=True)
    password = Column(String(64), nullable=False)
    email = Column(String(64), nullable=False, index=True)
    articles = relationship("Article")

    def __repr__(self):
        return '%s' % self.__class__.__name__


class Article(Base):
    __tablename__ = 'Article'
    id = Column(Integer, primary_key=True)
    title = Column(String(255), nullable=False, index=True)
    content = Column(Text)
    user_id = Column(Integer, ForeignKey('User.id'))
    user = relationship('User')

    def __repr__(self):
        return '%s' % self.__class__.__name__

• nullable 是否允许字段为null ，False
• index ：是否建立索引
• relationship 只是维护关系，表中并无体现实际字段 ，内容相互关联的表
• ForeignKey： 为定义外键，内容为相互关联的外键字段，注意与__tablename__中内容相符合

一对一关系

6. 一对一关系

一个用户User有唯一的扩展信息。我们可以把它们放到另一张 UserInfo 表中，关系是一对一

backref： 可以单边维护关系，两边不需要同时写relationship

class UserInfo(Base):

    __tablename__ = 'userinfo'

    id = Column(Integer, primary_key=True)
    name = Column(String(64))
    qq = Column(String(11))
    phone = Column(String(11))
    link = Column(String(64))
    user_id = Column(Integer, ForeignKey('User.id'))
    
class User(Base):
    __tablename__ = "User"
    id = Column(Integer, primary_key=True)
    username = Column(String(64), nullable=False, index=True)
    password = Column(String(64), nullable=False)
    email = Column(String(64), nullable=False, index=True)
    articles = relationship("Article")
    articles = relationship("UserInfo",backref=False,uselist=False)

    def __repr__(self):
        return '%s' % self.__class__.__name__

多对多关系

7. 多对多关系

标签与博客之间就是一个多对多的关系，需要引入第三张表来存放，两则之间的关系。

# 为中间表
article_tag = Table(
    'article_tag', Base.metadata,
    Column('article_id', Integer, ForeignKey('Article.id')),
    Column('tag_id', Integer, ForeignKey('Tag.id'))
)

class Tag(Base):
    __tablename__ = 'Tag'

    id = Column(Integer, primary_key=True)
    name = Column(String(64), nullable=False, index=True)

    def __repr__(self):
        return '%s(%r)' % (self.__class__.__name__, self.name)

8. 基本操作s

9. # coding = utf-8
   
   # coding = utf-8
   from sqlalchemy import create_engine, ForeignKey, Table
   from sqlalchemy.ext.declarative import declarative_base
   from sqlalchemy import Column, Integer, String, Text, Float, Date, DateTime
   from sqlalchemy.orm import relationship
   from sqlalchemy.orm import sessionmaker
   
   mysql_sql = "mysql+mysqldb://root:root@localhost:3306/test?charset=utf8"
   
   engine = create_engine(mysql_sql)
   Base = declarative_base()
   
   
   class Car(Base):
       __tablename__ = "Cars"
   
       Id = Column(Integer, primary_key=True)
       Name = Column(String(25))
       Price = Column(Integer)
   
       def __repr__(self):
           return  "%s %s %s %s"% (self.__class__.__name__,self.Id,self.Name,self.Price)
   
   
   Base.metadata.bind = engine
   Base.metadata.create_all(engine)
   
   Session = sessionmaker(bind=engine)
   session = Session()
   
   # 插入数据
   # session.add_all(
   #     [Car(Id=1, Name='Audi', Price=52642),
   #      Car(Id=2, Name='Mercedes', Price=57127),
   #      Car(Id=3, Name='Skoda', Price=9000),
   #      Car(Id=4, Name='Volvo', Price=29000),
   #      Car(Id=5, Name='Bentley', Price=350000),
   #      Car(Id=6, Name='Citroen', Price=21000),
   #      Car(Id=7, Name='Hummer', Price=41400),
   #      Car(Id=8, Name='Volkswagen', Price=21600)])
   # session.commit()
   
   # 查询所有
   rs = session.query(Car).all()
   for x in rs:
       print(x)
   # 查询第一次数据数据
   rs1 = session.query(Car).get(1)
   print(rs1)
   
   # 增加一个数据
   c1 = Car(Name="dongfeng",Price="255000")
   session.add(c1)
   session.commit()
   
   # 过滤数据 条件查询 谓词
   
   c2 = session.query(Car).filter(Car.Name.like("V%"))
   print(c2) # 查看Sql
   print(c2.all())
   
   # 删除
   c3 = session.query(Car).filter(Car.Id.in_([1]))
   print("c3:%s",c3)
   session.delete(c3)