SQLAlchemy 进阶

SQLAlchemy使用

1、执行原生SQL语句

from sqlalchemy.orm import sessionmaker

from sqlalchemy import create_engine

from sqlalchemy.orm import scoped_session

from models import Student,Course,Student2Course

engine = create_engine(

		"mysql+pymysql://root:123456@127.0.0.1:3306/s9day120?charset=utf8",

		max_overflow=0,  # 超过连接池大小外最多创建的连接

		pool_size=5,  # 连接池大小

		pool_timeout=30,  # 池中没有线程最多等待的时间，否则报错

		pool_recycle=-1  # 多久之后对线程池中的线程进行一次连接的回收（重置）

	)

SessionFactory = sessionmaker(bind=engine)

session = scoped_session(SessionFactory)

def task():

	""""""

	# 方式一：

	"""

	# 查询

	# cursor = session.execute('select * from users')

	# result = cursor.fetchall()

	# 添加

	cursor = session.execute('INSERT INTO users(name) VALUES(:value)', params={"value": 'wupeiqi'})

	session.commit()

	print(cursor.lastrowid)

	"""

	# 方式二：

	"""

	# conn = engine.raw_connection()

	# cursor = conn.cursor()

	# cursor.execute(

	#     "select * from t1"

	# )

	# result = cursor.fetchall()

	# cursor.close()

	# conn.close()

	"""

	# 将连接交还给连接池

	session.remove()

from threading import Thread

for i in range(20):

	t = Thread(target=task)

	t.start()

2、创建数据库表

#!/usr/bin/env python

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

import datetime

from sqlalchemy import create_engine

from sqlalchemy.ext.declarative import declarative_base

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

from sqlalchemy.orm import relationship

Base = declarative_base()

# ##################### 单表示例 #########################

class Users(Base):

    __tablename__ = 'users'

    id = Column(Integer, primary_key=True)

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

    age = Column(Integer, default=18)

    email = Column(String(32), unique=True)

    ctime = Column(DateTime, default=datetime.datetime.now)

    extra = Column(Text, nullable=True)

    __table_args__ = (

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

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

    )

class Hosts(Base):

    __tablename__ = 'hosts'

    id = Column(Integer, primary_key=True)

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

    ctime = Column(DateTime, default=datetime.datetime.now)

# ##################### 一对多示例 #########################

class Hobby(Base):

    __tablename__ = 'hobby'

    id = Column(Integer, primary_key=True)

    caption = Column(String(50), default='篮球')

class Person(Base):

    __tablename__ = 'person'

    nid = Column(Integer, primary_key=True)

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

    hobby_id = Column(Integer, ForeignKey("hobby.id"))

    # 与生成表结构无关，仅用于查询方便

    hobby = relationship("Hobby", backref='pers')

# ##################### 多对多示例 #########################

class Server2Group(Base):

    __tablename__ = 'server2group'

    id = 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)

    # 与生成表结构无关，仅用于查询方便

    servers = relationship('Server', secondary='server2group', backref='groups')

class Server(Base):

    __tablename__ = 'server'

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

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

def init_db():

    """

    根据类创建数据库表

    :return:

    """

    engine = create_engine(

        "mysql+pymysql://root:123@127.0.0.1:3306/s6?charset=utf8",

        max_overflow=0,  # 超过连接池大小外最多创建的连接

        pool_size=5,  # 连接池大小

        pool_timeout=30,  # 池中没有线程最多等待的时间，否则报错

        pool_recycle=-1  # 多久之后对线程池中的线程进行一次连接的回收（重置）

    )

    Base.metadata.create_all(engine)

def drop_db():

    """

    根据类删除数据库表

    :return:

    """

    engine = create_engine(

        "mysql+pymysql://root:123@127.0.0.1:3306/s6?charset=utf8",

        max_overflow=0,  # 超过连接池大小外最多创建的连接

        pool_size=5,  # 连接池大小

        pool_timeout=30,  # 池中没有线程最多等待的时间，否则报错

        pool_recycle=-1  # 多久之后对线程池中的线程进行一次连接的回收（重置）

    )

    Base.metadata.drop_all(engine)

if __name__ == '__main__':

    drop_db()

    init_db()

方式一：

from sqlalchemy.orm import sessionmaker

from sqlalchemy import create_engine

from models import Student,Course,Student2Course

engine = create_engine(

        "mysql+pymysql://root:123456@127.0.0.1:3306/s9day120?charset=utf8",

        max_overflow=0,  # 超过连接池大小外最多创建的连接

        pool_size=5,  # 连接池大小

        pool_timeout=30,  # 池中没有线程最多等待的时间，否则报错

        pool_recycle=-1  # 多久之后对线程池中的线程进行一次连接的回收（重置）

    )

SessionFactory = sessionmaker(bind=engine)

def task():

    # 去连接池中获取一个连接

    session = SessionFactory()

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

    # 将连接交还给连接池

    session.close()

from threading import Thread

for i in range(20):

    t = Thread(target=task)

    t.start()

方式二：（推荐，基于Threading.local实现）

from sqlalchemy.orm import sessionmaker

from sqlalchemy import create_engine

from sqlalchemy.orm import scoped_session

from models import Student,Course,Student2Course

engine = create_engine(

        "mysql+pymysql://root:123456@127.0.0.1:3306/s9day120?charset=utf8",

        max_overflow=0,  # 超过连接池大小外最多创建的连接

        pool_size=5,  # 连接池大小

        pool_timeout=30,  # 池中没有线程最多等待的时间，否则报错

        pool_recycle=-1  # 多久之后对线程池中的线程进行一次连接的回收（重置）

    )

SessionFactory = sessionmaker(bind=engine)

session = scoped_session(SessionFactory)

def task():

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

    # 将连接交还给连接池

    session.remove()

from threading import Thread

for i in range(20):

    t = Thread(target=task)

    t.start()

连接的两种方式

#!/usr/bin/env python

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

from sqlalchemy.orm import sessionmaker

from sqlalchemy import create_engine

from sqlalchemy.orm import scoped_session

from models import Users

engine = create_engine("mysql+pymysql://root:123@127.0.0.1:3306/s6", max_overflow=0, pool_size=5)

Session = sessionmaker(bind=engine)

"""

# 线程安全，基于本地线程实现每个线程用同一个session

# 特殊的：scoped_session中有原来方法的Session中的一下方法：

public_methods = (

    '__contains__', '__iter__', 'add', 'add_all', 'begin', 'begin_nested',

    'close', 'commit', 'connection', 'delete', 'execute', 'expire',

    'expire_all', 'expunge', 'expunge_all', 'flush', 'get_bind',

    'is_modified', 'bulk_save_objects', 'bulk_insert_mappings',

    'bulk_update_mappings',

    'merge', 'query', 'refresh', 'rollback',

    'scalar'

)

"""

session = scoped_session(Session)

# ############# 执行ORM操作 #############

obj1 = Users(name="alex1")

session.add(obj1)

# 提交事务

session.commit()

# 关闭session

session.close()

基于scoped_session实现线程安全

#!/usr/bin/env python

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

import time

import threading

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

from db import Users

engine = create_engine("mysql+pymysql://root:123@127.0.0.1:3306/s6", max_overflow=0, pool_size=5)

Session = sessionmaker(bind=engine)

def task(arg):

    session = Session()

    obj1 = Users(name="alex1")

    session.add(obj1)

    session.commit()

for i in range(10):

    t = threading.Thread(target=task, args=(i,))

    t.start()

多线程执行示例

#!/usr/bin/env python

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

import time

import threading

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

from sqlalchemy.sql import text

from sqlalchemy.engine.result import ResultProxy

from db import Users, Hosts

engine = create_engine("mysql+pymysql://root:123@127.0.0.1:3306/s6", max_overflow=0, pool_size=5)

Session = sessionmaker(bind=engine)

session = Session()

# 查询

# cursor = session.execute('select * from users')

# result = cursor.fetchall()

# 添加

cursor = session.execute('insert into users(name) values(:value)',params={"value":'wupeiqi'})

session.commit()

print(cursor.lastrowid)

session.close()

原生sql语句

#!/usr/bin/env python

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

import time

import threading

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

from sqlalchemy.sql import text

from sqlalchemy.engine.result import ResultProxy

from db import Users, Hosts, Hobby, Person

engine = create_engine("mysql+pymysql://root:123@127.0.0.1:3306/s6?charset=utf8", max_overflow=0, pool_size=5)

Session = sessionmaker(bind=engine)

session = Session()

# 添加

"""

session.add_all([

    Hobby(caption='乒乓球'),

    Hobby(caption='羽毛球'),

    Person(name='张三', hobby_id=3),

    Person(name='李四', hobby_id=4),

])

person = Person(name='张九', hobby=Hobby(caption='姑娘'))

session.add(person)

hb = Hobby(caption='人妖')

hb.pers = [Person(name='文飞'), Person(name='博雅')]

session.add(hb)

session.commit()

"""

# 使用relationship正向查询

"""

v = session.query(Person).first()

print(v.name)

print(v.hobby.caption)

"""

# 使用relationship反向查询

"""

v = session.query(Hobby).first()

print(v.caption)

print(v.pers)

"""

session.close()

基于relationship操作ForeignKey

#!/usr/bin/env python

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

import time

import threading

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

from sqlalchemy.sql import text

from sqlalchemy.engine.result import ResultProxy

from db import Users, Hosts, Hobby, Person, Group, Server, Server2Group

engine = create_engine("mysql+pymysql://root:123@127.0.0.1:3306/s6?charset=utf8", max_overflow=0, pool_size=5)

Session = sessionmaker(bind=engine)

session = Session()

# 添加

"""

session.add_all([

    Server(hostname='c1.com'),

    Server(hostname='c2.com'),

    Group(name='A组'),

    Group(name='B组'),

])

session.commit()

s2g = Server2Group(server_id=1, group_id=1)

session.add(s2g)

session.commit()

gp = Group(name='C组')

gp.servers = [Server(hostname='c3.com'),Server(hostname='c4.com')]

session.add(gp)

session.commit()

ser = Server(hostname='c6.com')

ser.groups = [Group(name='F组'),Group(name='G组')]

session.add(ser)

session.commit()

"""

# 使用relationship正向查询

"""

v = session.query(Group).first()

print(v.name)

print(v.servers)

"""

# 使用relationship反向查询

"""

v = session.query(Server).first()

print(v.hostname)

print(v.groups)

"""

session.close()

基于relationship操作m2m

#!/usr/bin/env python

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

import time

import threading

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

from sqlalchemy.sql import text, func

from sqlalchemy.engine.result import ResultProxy

from db import Users, Hosts, Hobby, Person, Group, Server, Server2Group

engine = create_engine("mysql+pymysql://root:123@127.0.0.1:3306/s6?charset=utf8", max_overflow=0, pool_size=5)

Session = sessionmaker(bind=engine)

session = Session()

# 关联子查询

subqry = session.query(func.count(Server.id).label("sid")).filter(Server.id == Group.id).correlate(Group).as_scalar()

result = session.query(Group.name, subqry)

"""

SELECT `group`.name AS group_name, (SELECT count(server.id) AS sid

FROM server

WHERE server.id = `group`.id) AS anon_1

FROM `group`

"""

# 原生SQL

"""

# 查询

cursor = session.execute('select * from users')

result = cursor.fetchall()

# 添加

cursor = session.execute('insert into users(name) values(:value)',params={"value":'wupeiqi'})

session.commit()

print(cursor.lastrowid)

"""

session.close()

其他

SQLAlchemy 进阶的更多相关文章

Python菜鸟之路：sqlalchemy/paramiko进阶
前言:ORM中的两种创建方式数据库优先:指的是先创建数据库,包括表和字段的建立,然后根据数据库生成ORM的代码,它是先创建数据库,再创建相关程序代码代码优先:就是先写代码,然后根据代码去生成数据库 ...
(转)SQLAlchemy入门和进阶
URL:https://zhuanlan.zhihu.com/p/27400862 https://www.cnblogs.com/mrchige/p/6389588.html---SQLAlchem ...
day95:flask:SQLAlchemy数据库查询进阶&关联查询
目录 1.数据库查询-进阶 1.常用的SQLAlchemy查询过滤器 2.常用的SQLAlchemy查询结果的方法 3.filter 4.order_by 5.count 6.limit&of ...
python 学习笔记十一 SQLALchemy ORM(进阶篇)
SqlAlchemy ORM 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A ...
sqlalchemy ORM进阶－批量插入数据
参考: https://www.jb51.net/article/49789.htm https://blog.csdn.net/littlely_ll/article/details/8270687 ...
Tornado sqlalchemy
上篇文章提到了,最近在用 Python 做一个网站.除了 Tornado ,主要还用到了 SQLAlchemy.这篇就是介绍我在使用 SQLAlchemy 的过程中,学到的一些知识. 首先说下,由于最 ...
【Python】 SQLAlchemy的初步使用
SQLAlchemy 在很多Python的web框架中都整合进了SQLAlchemy这个主要发挥ORM作用的模块.所谓ORM,就是把复杂的SQL语句给包装成更加面向对象,易于理解的样子.在操作数据库的 ...
Flask进阶
Threading.local 作用:为每个线程创建一个独立的空间,使得线程对自己的空间中的数据进行操作(数据隔离). 应用: flask上下文管理中的local中比这更高级,为协程. DBUtils ...
SQLAlchemy（包含有Flask-Migrate知识点）
what's the SQLAlchemy SQLAlchemy是一个基于Python实现的ORM框架.该框架建立在 DB API之上,使用关系对象映射进行数据库操作,简言之便是:将类和对象转换成SQ ...

随机推荐

Robot Framework接口测试（1）
RF是做接口测试的一个非常方便的工具,我们只需要写好发送报文的脚本,就可以灵活的对接口进行测试. 做接口测试我们需要做如下工作: 1.拼接发送的报文 2.发送请求的方法 3.对结果进行判断我们先按步 ...
verilog中task的用法
任务就是一段封装在“task-endtask”之间的程序.任务是通过调用来执行的,而且只有在调用时才执行,如果定义了任务,但是在整个过程中都没有调用它,那么这个任务是不会执行的.调用某个任务时可能需要 ...
Maven build标签
前言: <build >设置,主要用于编译设置 1.分类在Maven的pom.xml文件中,存在如下两种<build>: (1)全局配置(project build) 针对整 ...
GZip压缩与解压缩
GZIP的压缩与解压缩代码: public static class CompressionHelper { /// <summary> /// Compress the byte[] / ...
YII框架安装过程-数据库访问
1.电脑上原来安装了phpstudy.关掉phpstudy,启动wamp,虽启动成功,但仍然无法使用phpmyadmin登录数据库管理页面. 2.查看到系统服务有mysql服务,检查属性均为emsoa ...
java图形用户界面添加背景颜色不成功的解决方案
总结:背景颜色不成功,那么使用这个方法试试.getContentpane(); package clientFrame; import java.awt.Color; import java.awt. ...
temp3
leetcode796
public class Solution { public bool RotateString(string A, string B) { string temp = A; int len = A. ...
Python基础学习四函数
1.内置函数 Python内置了很多有用的函数,是可以直接调用的. 参考链接:https://docs.python.org/3/library/functions.html 调用函数的时候,如果传入 ...
windows命令行查询/kill 进程
查询: tasklist kill对应进程按名称:taskkill /im xxx.exe 按pid: taskill /pid pid kill掉xxx进程的相关进程(子进程) taskkill ...

SQLAlchemy 进阶

SQLAlchemy使用

1、执行原生SQL语句

2、创建数据库表

SQLAlchemy 进阶的更多相关文章

随机推荐

热门专题