SQLAlchemy是Python编程语言下的一款ORM框架，该框架建立在数据库API之上，使用关系对象映射进行数据库操作，简言之便是：将对象转换成SQL，然后使用数据API执行SQL并获取执行结果。

SQLAlchemy本身无法操作数据库，其必须以来pymsql等第三方插件，Dialect用于和数据API进行交流，根据配置文件的不同调用不同的数据库API，从而实现对数据库的操作.

MySQL-Python

    mysql+mysqldb://<user>:<password>@<host>[:<port>]/<dbname>

pymysql

    mysql+pymysql://<username>:<password>@<host>/<dbname>[?<options>]

MySQL-Connector

    mysql+mysqlconnector://<user>:<password>@<host>[:<port>]/<dbname>

cx_Oracle

    oracle+cx_oracle://user:pass@host:port/dbname[?key=value&key=value...]

更多详见：http://docs.sqlalchemy.org/en/latest/dialects/index.html

底层处理

使用 Engine/ConnectionPooling/Dialect 进行数据库操作，Engine使用ConnectionPooling连接数据库，然后再通过Dialect执行SQL语句。

#!/usr/bin/env python

# -*- coding:utf-8 -*-

from sqlalchemy import create_engine

engine = create_engine("mysql+pymysql://root:123@127.0.0.1:3306/t1", max_overflow=5)

# 执行SQL

# cur = engine.execute(

#     "INSERT INTO hosts (host, color_id) VALUES ('1.1.1.22', 3)"

# )

# 新插入行自增ID

# cur.lastrowid

# 执行SQL

# cur = engine.execute(

#     "INSERT INTO hosts (host, color_id) VALUES(%s, %s)",[('1.1.1.22', 3),('1.1.1.221', 3),]

# )

# 执行SQL

# cur = engine.execute(

#     "INSERT INTO hosts (host, color_id) VALUES (%(host)s, %(color_id)s)",

#     host='1.1.1.99', color_id=3

# )

# 执行SQL

# cur = engine.execute('select * from hosts')

# 获取第一行数据

# cur.fetchone()

# 获取第n行数据

# cur.fetchmany(3)

# 获取所有数据

# cur.fetchall()

说白了就是使用pymysql的方法一样.

ORM功能使用

创建表

from sqlalchemy.ext.declarative import declarative_base

from sqlalchemy import Column, Integer, String, ForeignKey, UniqueConstraint, Index

from sqlalchemy.orm import sessionmaker, relationship

from sqlalchemy import create_engine

engine = create_engine("mysql+pymysql://root:7ujm8ik,@192.168.4.193:3306/testsql", max_overflow=5)

Base = declarative_base()

# 创建单表

class Users(Base):

    __tablename__ = 'users'

    id = Column(Integer, primary_key=True)

    name = Column(String(32))

    extra = Column(String(16))

    __table_args__ = (

    UniqueConstraint('id', 'name', name='uix_id_name'),

        Index('ix_id_name', 'name', 'extra'),

    )

# 一对多

class Favor(Base):

    __tablename__ = 'favor'

    nid = Column(Integer, primary_key=True)

    caption = Column(String(50), default='red', unique=True)

class Person(Base):

    __tablename__ = 'person'

    nid = Column(Integer, primary_key=True)

    name = Column(String(32), index=True, nullable=True)

    favor_id = Column(Integer, ForeignKey("favor.nid"))

# 多对多

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'))

class Group(Base):

    __tablename__ = 'group'

    id = Column(Integer, primary_key=True)

    name = Column(String(64), unique=True, nullable=False)

class Server(Base):

    __tablename__ = 'server'

    id = Column(Integer, primary_key=True, autoincrement=True)

    hostname = Column(String(64), unique=True, nullable=False)

    port = Column(Integer, default=22)

#定义初始化数据库函数

def init_db():

    Base.metadata.create_all(engine)

#顶固删除数据库函数

def drop_db():

    Base.metadata.drop_all(engine)

# drop_db()

init_db()

操作表

操作后我们会发现,class定义的为首字母大写,写入表以后为全部小写的模式.

from sqlalchemy.ext.declarative import declarative_base

from sqlalchemy import Column, Integer, String, ForeignKey, UniqueConstraint, Index

from sqlalchemy.orm import sessionmaker, relationship

from sqlalchemy import create_engine

engine = create_engine("mysql+pymysql://root:7ujm8ik,@192.168.4.193:3306/testsql", max_overflow=5)

Base = declarative_base()

# 创建单表

class Users(Base):

    __tablename__ = 'users'

    id = Column(Integer, primary_key=True)

    name = Column(String(32))

    extra = Column(String(16))

    __table_args__ = (

    UniqueConstraint('id', 'name', name='uix_id_name'),

        Index('ix_id_name', 'name', 'extra'),

    )

# 一对多

class Favor(Base):

    __tablename__ = 'favor'

    nid = Column(Integer, primary_key=True)

    caption = Column(String(50), default='red', unique=True)

class Person(Base):

    __tablename__ = 'person'

    nid = Column(Integer, primary_key=True)

    name = Column(String(32), index=True, nullable=True)

    favor_id = Column(Integer, ForeignKey("favor.nid"))

# 多对多

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'))

class Group(Base):

    __tablename__ = 'group'

    id = Column(Integer, primary_key=True)

    name = Column(String(64), unique=True, nullable=False)

class Server(Base):

    __tablename__ = 'server'

    id = Column(Integer, primary_key=True, autoincrement=True)

    hostname = Column(String(64), unique=True, nullable=False)

    port = Column(Integer, default=22)

#定义初始化数据库函数

def init_db():

    Base.metadata.create_all(engine)

#顶固删除数据库函数

def drop_db():

    Base.metadata.drop_all(engine)

# drop_db()

# init_db()

#创建mysql操作对象

Session = sessionmaker(bind=engine)

session = Session()

增

add:增加一个
add_all:增加多个

Session = sessionmaker(bind=engine)

session = Session()

obj = Users(name='alex',extra='sb')

session.add(obj)

#add_all 列表形式

session.add_all([

    Users(name='cc',extra='cow'),

    Users(name='dd',extra='cowcow')

])

#提交

session.commit()

删

# 删

session.query(Users).filter(Users.id > 2).delete()

# 提交

session.commit()

改

session.query(Users).filter(Users.id > 2).update({"name" : "099"})

session.query(Users).filter(Users.id > 2).update({Users.name: Users.name + "099"}, synchronize_session=False)

session.query(Users).filter(Users.id > 2).update({"num": Users.num + 1}, synchronize_session="evaluate")

session.commit()

# 提交

session.commit()

查

ret=session.query(Users).all()

ret = session.query(Users.id, Users.extra).all()    #结果为一个列表

ret = session.query(Users).filter_by(name='cc').first()

ret = session.query(Users).filter_by(name='cc').all()

print(type(ret))

print(ret[0].extra)

其他

条件:

#　条件

ret = session.query(Users).filter_by(name='alex').all()

ret = session.query(Users).filter(Users.id > 1, Users.name == 'eric').all()

ret = session.query(Users).filter(Users.id.between(1, 3), Users.name == 'eric').all()

ret = session.query(Users).filter(Users.id.in_([1,3,4])).all()

ret = session.query(Users).filter(~Users.id.in_([1,3,4])).all()

ret = session.query(Users).filter(Users.id.in_(session.query(Users.id).filter_by(name='eric'))).all()

与 或:

from sqlalchemy import and_, or_

ret = session.query(Users).filter(and_(Users.id > 3, Users.name == 'eric')).all()

ret = session.query(Users).filter(or_(Users.id < 2, Users.name == 'eric')).all()

ret = session.query(Users).filter(

    or_(

        Users.id < 2,

        and_(Users.name == 'eric', Users.id > 3),

        Users.extra != ""

    )).all()

通配符 非:

ret = session.query(Users).filter(Users.name.like('e%')).all()

ret = session.query(Users).filter(~Users.name.like('e%')).all()

限制:

ret = session.query(Users)[1:2]

排序:

ret = session.query(Users).order_by(Users.name.desc()).all()

ret = session.query(Users).order_by(Users.name.desc(), Users.id.asc()).all()

分组:

from sqlalchemy.sql import func

ret = session.query(Users).group_by(Users.extra).all()

ret = session.query(

    func.max(Users.id),

    func.sum(Users.id),

    func.min(Users.id)).group_by(Users.name).all()

ret = session.query(

    func.max(Users.id),

    func.sum(Users.id),

    func.min(Users.id)).group_by(Users.name).having(func.min(Users.id) >2).all()

连表:

ret = session.query(Users, Favor).filter(Users.id == Favor.nid).all()

ret = session.query(Person).join(Favor).all()

ret = session.query(Person).join(Favor, isouter=True).all()

组合:

q1 = session.query(Users.name).filter(Users.id > 2)

q2 = session.query(Favor.caption).filter(Favor.nid < 2)

ret = q1.union(q2).all()

q1 = session.query(Users.name).filter(Users.id > 2)

q2 = session.query(Favor.caption).filter(Favor.nid < 2)

ret = q1.union_all(q2).all()

下载PDF文档

 
 

最新文章

  1. jquery更改加载图片大小
  2. NOIP2013pj小朋友的数字[DP 最大子段和]
  3. linux基础-附件1 linux系统启动流程
  4. bash 截取字符串
  5. 转：并查集总结 例题：hdoj 1232 畅通工程
  6. 宣布发布长期保留 Azure Backup功能
  7. C++ socket开发1
  8. 用标准版的Eclipse搭建PHP环境
  9. mac下升级ruby环境版本
  10. QThread 与 QObject的关系（QObject可以用于多线程，可以发送信号调用存在于其他线程的slot函数，但GUI类不可重入）
  11. linux开机自启动服务优化设置命令
  12. jdk动态代理与cglib代理、spring aop代理实现原理解析
  13. JSP Cookie的使用
  14. font-size:100% 原因
  15. Codeforces Round #538 (Div. 2) C. Trailing Loves (or L&#39;oeufs?) (分解质因数)
  16. dubbo Framework pic
  17. GridView“GridView1”激发了未处理的事件“RowDeleting”
  18. delphi TStringList 用法详解
  19. Echarts服务端生成图片
  20. UnicodeEncodeError: &#39;gbk&#39; codec can&#39;t encode character &#39;\xbb&#39; in position 0: illegal multibyte sequence

热门文章

  1. KMP算法——Javascript实现
  2. 用LinkedHashMap实现LRU算法
  3. #用Python直接写UTF-8文本文件
  4. 使用aspose.word两句代码将word转换为pdf
  5. .NET文件上传的大小限制配置
  6. 利用HTML5开发Android(4)---HTML5本地存储之Web Storage
  7. hotfix分析
  8. http://www.jobui.com/mianshiti/it/java/6782/
  9. C#读写者线程（用AutoResetEvent实现同步）
  10. SGU 532. Building Foundation 暴力