SQLAlchemy

一. 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，简言之便是：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。

1
pip3 install sqlalchemy

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，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...]

更多：http://docs.sqlalchemy.org/en/latest/dialects/index.htm

二. 使用

1. 执行原生SQL语句

mport 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()

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 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%';

解决重复链接：---------------上下文

from utils.pool import db_pool
import pymysqlclass SQLHelper(object):def __init__(self):self.conn = Noneself.cursor = Nonedef open(self,cursor=pymysql.cursors.DictCursor):self.conn = db_pool.POOL.connection()self.cursor = self.conn.cursor(cursor=cursor)def close(self):self.cursor.close()self.conn.close()def fetchone(self,sql,params):cursor = self.cursorcursor.execute(sql,params)result = cursor.fetchone()return resultdef fetchall(self, sql, params):cursor = self.cursorcursor.execute(sql, params)result = cursor.fetchall()return resultdef __enter__(self):self.open()return selfdef __exit__(self, exc_type, exc_val, exc_tb):self.close()# with SQLHelper() as obj:
#
#     print(obj)
#     print('正在执行')

sqlhelper

#!/usr/bin/env python
# -*- coding:utf-8 -*-
from flask import Blueprint, request, render_template, redirect, session,current_app
from utils.pool import db_pool
from utils.pool.sqlhelper import SQLHelper
account = Blueprint('account', __name__)
@account.route('/login', methods=['GET', 'POST'])
def login():if request.method == 'GET':return render_template('login.html')else:# 方式一# helper = SQLHelper()# helper.open()# result = helper.fetchone('select * from users where name=%s and pwd = %s',[request.form.get('user'),request.form.get('pwd'),])# helper.close()# 方式二：with SQLHelper() as helper:result = helper.fetchone('select * from users where name=%s and pwd = %s',[request.form.get('user'),request.form.get('pwd'),])if result:current_app.auth_manager.login(result['name'])return redirect('/index')return render_template('login.html')

account

注册cession:
　

class BaseConfig(object):SESSION_TYPE = 'redis'  # session类型为redisSESSION_KEY_PREFIX = 'session:'  # 保存到session中的值的前缀SESSION_PERMANENT = False  # 如果设置为True，则关闭浏览器session就失效。SESSION_USE_SIGNER = False  # 是否对发送到浏览器上 session:cookie值进行加密

查看radisa中的值：

import redis
conn = redis.Redis(host='47.93.4.198', port=6379, password='123123')  # 用于连接redis的配置
v = conn.keys()
print(v)

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 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

View Code

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()

View Code

#!/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

多线程执行实例

#!/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

#　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()
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
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 funcret = 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()常用操作

基本操作

#!/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

#!/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

#!/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

#!/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

转载于:https://www.cnblogs.com/w-s-l123/p/8268699.html

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