一、SQLAlchemy介绍

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。

将类和对象转换成SQL，然后使用数据API执行SQL并获取执行结果。

二、组成部分

Engine，框架的引擎

Connection Pooling，数据库连接池

Dialect，选择连接数据库的DB API种类

Schema/Types，架构和类型

SQL  Exprression Language，SQL表达式语言

SQLAlchemy本身无法操作数据库，其必须用pymysql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，如：

MySQL-Pythonmysql+mysqldb://<user>:<password>@<host>[:<port>]/<dbname>pymysqlmysql+pymysql://<username>:<password>@<host>/<dbname>[?<options>]MySQL-Connectormysql+mysqlconnector://<user>:<password>@<host>[:<port>]/<dbname>cx_Oracleoracle+cx_oracle://user:pass@host:port/dbname[?key=value&key=value...]

二、使用

1.执行原生SQL语句

import time
import threading
import sqlalchemy
from sqlalchemy import create_engine
from sqlalchemy.engine.base import Engineengine = create_engine("mysql+pymysql://root:123@127.0.0.1:3306/t1?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）
)def task(arg):conn = engine.raw_connection()cursor = conn.cursor()cursor.execute("select * from t1")result = cursor.fetchall()cursor.close()conn.close()for i in range(20):t = threading.Thread(target=task, args=(i,))t.start()

#!/usr/bin/env python
# -*- coding:utf-8 -*-
import time
import threading
import sqlalchemy
from sqlalchemy import create_engine
from sqlalchemy.engine.base import Engineengine = create_engine("mysql+pymysql://root:123@127.0.0.1:3306/t1", max_overflow=0, pool_size=5)def task(arg):conn = engine.contextual_connect()with conn:cur = conn.execute("select * from t1")result = cur.fetchall()print(result)for i in range(20):t = threading.Thread(target=task, args=(i,))t.start()

View Code

#!/usr/bin/env python
# -*- coding:utf-8 -*-
import time
import threading
import sqlalchemy
from sqlalchemy import create_engine
from sqlalchemy.engine.base import Engine
from sqlalchemy.engine.result import ResultProxy
engine = create_engine("mysql+pymysql://root:123@127.0.0.1:3306/t1", max_overflow=0, pool_size=5)def task(arg):cur = engine.execute("select * from t1")result = cur.fetchall()cur.close()print(result)for i in range(20):t = threading.Thread(target=task, args=(i,))t.start()

View Code

注意: 查看连接 show status like 'Threads%';

2.ORM

 a.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, IndexBase = declarative_base()class Users(Base):__tablename__ = 'users'id = Column(Integer, primary_key=True)name = Column(String(32), index=True, nullable=False)# 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', 'email'),
    )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()创建单表创建单表

View Code

#!/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 relationshipBase = 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()创建多个表并包含Fk、M2M关系创建多个表并包含Fk、M2M关系

创建多个表并包含Fk、M2M关系

指定关联列：hobby = relationship("Hobby", backref='pers',foreign_keys="Person.hobby_id")

b.操作数据库表

#!/usr/bin/env python
# -*- coding:utf-8 -*-
from sqlalchemy.orm import sessionmaker
from sqlalchemy import create_engine
from models import Usersengine = create_engine("mysql+pymysql://root:123@127.0.0.1:3306/s6", max_overflow=0, pool_size=5)
Session = sessionmaker(bind=engine)# 每次执行数据库操作时，都需要创建一个session
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()

3.基于scoped_session实现线程安全

#!/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 Usersengine = 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实现线程安全基于scoped_session实现线程安全

基于scoped_session实现线程安全

4.多线程执行示例

#!/usr/bin/env python
# -*- coding:utf-8 -*-
import time
import threadingfrom 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 Usersengine = 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()多线程执行示例多线程执行示例

多线程执行示例

5.基本增删改查示例

#!/usr/bin/env python
# -*- coding:utf-8 -*-
import time
import threadingfrom 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 textfrom db import Users, Hostsengine = create_engine("mysql+pymysql://root:123@127.0.0.1:3306/s6", max_overflow=0, pool_size=5)
Session = sessionmaker(bind=engine)session = Session()# ################ 添加 ################
"""
obj1 = Users(name="wupeiqi")
session.add(obj1)session.add_all([Users(name="wupeiqi"),Users(name="alex"),Hosts(name="c1.com"),
])
session.commit()
"""# ################ 删除 ################
"""
session.query(Users).filter(Users.id > 2).delete()
session.commit()
"""
# ################ 修改 ################
"""
session.query(Users).filter(Users.id > 0).update({"name" : "099"})
session.query(Users).filter(Users.id > 0).update({Users.name: Users.name + "099"}, synchronize_session=False)
session.query(Users).filter(Users.id > 0).update({"age": Users.age + 1}, synchronize_session="evaluate")
session.commit()
"""
# ################ 查询 ################
"""
r1 = session.query(Users).all()
r2 = session.query(Users.name.label('xx'), Users.age).all()
r3 = session.query(Users).filter(Users.name == "alex").all()
r4 = session.query(Users).filter_by(name='alex').all()
r5 = session.query(Users).filter_by(name='alex').first()
r6 = session.query(Users).filter(text("id<:value and name=:name")).params(value=224, name='fred').order_by(Users.id).all()
r7 = session.query(Users).from_statement(text("SELECT * FROM users where name=:name")).params(name='ed').all()
"""session.close()基本增删改查示例基本增删改查示例

基本增删改查示例

6.常用操作

1. 指定列
select id,name as cname from users;
result = session.query(Users.id,Users.name.label('cname')).all()
for item in result:print(item[0],item.id,item.cname)2. 默认条件and
session.query(Users).filter(Users.id > 1, Users.name == 'eric').all()3. between
session.query(Users).filter(Users.id.between(1, 3), Users.name == 'eric').all()4. in
session.query(Users).filter(Users.id.in_([1,3,4])).all()
session.query(Users).filter(~Users.id.in_([1,3,4])).all()5. 子查询
session.query(Users).filter(Users.id.in_(session.query(Users.id).filter(Users.name=='eric'))).all()6. and 和 or
from sqlalchemy import and_, or_
session.query(Users).filter(Users.id > 3, Users.name == 'eric').all()
session.query(Users).filter(and_(Users.id > 3, Users.name == 'eric')).all()
session.query(Users).filter(or_(Users.id < 2, Users.name == 'eric')).all()
session.query(Users).filter(or_(Users.id < 2,and_(Users.name == 'eric', Users.id > 3),Users.extra != "")).all()7. filter_by
session.query(Users).filter_by(name='alex').all()8. 通配符
ret = session.query(Users).filter(Users.name.like('e%')).all()
ret = session.query(Users).filter(~Users.name.like('e%')).all()9. 切片
result = session.query(Users)[1:2]10.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()11. group by
om sqlalchemy.sql import funcret = session.query(Users.depart_id,func.count(Users.id),
).group_by(Users.depart_id).all()
for item in ret:print(item)from sqlalchemy.sql import funcret = session.query(Users.depart_id,func.count(Users.id),
).group_by(Users.depart_id).having(func.count(Users.id) >= 2).all()
for item in ret:print(item)12.union(上下联合，去重) 和 union all(上下联合，不去重)
"""
select id,name from users
UNION
select id,name from users;
"""
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()13.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()常用操作

常用操作

7.原生SQL语句

#!/usr/bin/env python
# -*- coding:utf-8 -*-
import time
import threadingfrom 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, Hostsengine = 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语句原生SQL语句

原生SQL语句

8.基于relationship操作ForeignKey

#!/usr/bin/env python
# -*- coding:utf-8 -*-
import time
import threadingfrom 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, Personengine = 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基于relationship操作ForeignKey

基于relationship操作ForeignKey

9.基于relationship操作m2m

#!/usr/bin/env python
# -*- coding:utf-8 -*-
import time
import threadingfrom 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, Server2Groupengine = 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基于relationship操作m2m

基于relationship操作m2m

10.其他

#!/usr/bin/env python
# -*- coding:utf-8 -*-
import time
import threadingfrom 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, Server2Groupengine = 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()其他其他

其他

转载于:https://www.cnblogs.com/tsboy/p/9210208.html

Flask--SQLAlchemy相关推荐

  1. flask sqlalchemy一对多关系详解

    下面的一对多关系以作者和文章为例: 首先创建一个文章表: class Post(db.Model): id = db.Column(db.Integer(),primary_key=True) tit ...

  2. alchemy php,Flask SQLAlchemy

    在Flask Web应用程序中使用原始SQL对数据库执行CRUD操作可能很乏味. 相反,Python工具包SQLAlchemy是一个功能强大的OR映射器,为应用程序开发人员提供了SQL的全部功能和灵活 ...

  3. Flask SQLAlchemy - 2013 Lost Connection

    Flask SQLAlchemy - 2013 Lost Connection 原因 mysql默认的连接超时时间为10s.由于路由字段没有加索引导致有时单条sql执行若超过10s,报了连接超时. 解 ...

  4. Flask – SQLAlchemy成员增加

    目录 简介 结构 展示 技术 运行 代码 创建数据库表单 views视图 home主页 添加成员addnew.html 展示页show_all 简介 结构 $ tree -I "__pyca ...

  5. python学习之flask sqlalchemy介绍和使用 表操作增删查改

    flask sqlalchemy介绍和使用 表操作增删查改 内容详细 1 sqlalchemy介绍和快速使用 1.1 介绍 # SQLAlchemy是一个基于Python实现的ORM框架# djang ...

  6. mysql报错1517_请教一下 flask+sqlalchemy+mysql 连接错误问题

    在本地调试 docker-compose 调试 mysql+nginx+flask 程序,报错(2003, "Can't connect to MySQL server on '127.0. ...

  7. mysql flaskalchemy_python flask sqlalchemy 数据库mysql操作

    第一步app.py: # coding=utf-8 import urllib from flask import Flask from werkzeug.routing import BaseCon ...

  8. flask+sqlalchemy+echarts动态显示数据

    一.创建测试数据 SET NAMES utf8mb4; SET FOREIGN_KEY_CHECKS = 0;-- ---------------------------- -- Table stru ...

  9. flask sqlalchemy wtf 使用笔记

    vip用户的model vip用户的model 这边 PlatUserFace 一定要写类名写表名会报错 获取用户信息 这里需要all 才能手动的去获取此用户Face的列表 vip用户的model 关 ...

  10. python3 flask sqlalchemy 数据库操作

    数据的查询 all():查询全部的数据,其结果是一个列表,每一个元素都是一个对象students = Student.query.all()过滤查询:第一种:filter,结果是baseQuery o ...

最新文章

  1. Python-Evoked地形图可视化
  2. 统计特性和概率估计-2 (数学推导与证明)
  3. atomic java_在Java中添加@atomic操作
  4. Visual Studio.net 2010 Windows Service 开发,安装与调试
  5. java 二进制文件 数据库_java从数据库中读取二进制文件并....
  6. java动态同步_java并发基础-Synchronized
  7. 【王牌选手分享】一发问鼎！鹅厂大神上分思路，助你玩转初赛！
  8. C#类对象转换成XML
  9. 百度指数查关键词（惊到我啦）
  10. premiere小tips（参考于干的教程）
  11. 语音处理基础：预加重、分帧、帧移、加窗、傅里叶变换
  12. 什么是SNP遗传力?
  13. C# - 习题07_计算1分2分5分硬币各有多少枚
  14. 如何实现表格固定表头和某列
  15. STM32F767---＞寄存器
  16. java计算机毕业设计智能医技预约系统源码+mysql数据库+系统+部署+lw文档
  17. Gent OS7乱码
  18. outlook显示无法当问ost文件
  19. IAR for ARM 无法烧写
  20. Unity和安卓（二）：接入 google 广告

热门文章

  1. 每天一道LeetCode-----找出给定序列的所有子序列
  2. 前后端分离项目后端向前端返回压缩包的方法实现java版
  3. K近邻法(KNN)原理小结
  4. HDU Problem - 4280 Island Transport（最大流）
  5. C/C++协程实现-学习笔记
  6. HTML下拉菜单去掉点,jQuery点击页面其他部分隐藏下拉菜单功能
  7. Leetcode题库 798.得分最高的最小轮调(差分数组 C实现)
  8. [BUUCTF-pwn]——ciscn_2019_ne_5
  9. 宿主机linux,宿主机上安装小linux
  10. 海思Hi3516DV300 SDK首次安装以及编译问题的解决