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Flask--SQLAlchemy

發布時間：2024/4/17 数据库 56 豆豆

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一、SQLAlchemy介紹

SQLAlchemy是一個基于Python實現的ORM框架。該框架建立在DB API之上，使用關系對象映射進行數據庫操作。

將類和對象轉換成SQL，然后使用數據API執行SQL并獲取執行結果。

二、組成部分

Engine，框架的引擎

Connection Pooling，數據庫連接池

Dialect，選擇連接數據庫的DB API種類

Schema/Types，架構和類型

SQL??Exprression Language，SQL表達式語言

SQLAlchemy本身無法操作數據庫，其必須用pymysql等第三方插件，Dialect用于和數據API進行交流，根據配置文件的不同調用不同的數據庫API，從而實現對數據庫的操作，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.執行原生SQL語句

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, # 超過連接池大小外最多創建的連接pool_size=5, # 連接池大小pool_timeout=30, # 池中沒有線程最多等待的時間，否則報錯pool_recycle=-1 # 多久之后對線程池中的線程進行一次連接的回收（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: 查看連接?show status like 'Threads%';

?2.ORM

?a.創建數據庫表

#!/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()# ##################### 單表示例 ######################### 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)# ##################### 一對多示例 ######################### class Hobby(Base):__tablename__ = 'hobby'id = Column(Integer, primary_key=True)caption = Column(String(50), default='籃球')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"))# 與生成表結構無關，僅用于查詢方便hobby = relationship("Hobby", backref='pers')# ##################### 多對多示例 #########################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)# 與生成表結構無關，僅用于查詢方便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():"""根據類創建數據庫表:return: """engine = create_engine("mysql+pymysql://root:123@127.0.0.1:3306/s6?charset=utf8",max_overflow=0, # 超過連接池大小外最多創建的連接pool_size=5, # 連接池大小pool_timeout=30, # 池中沒有線程最多等待的時間，否則報錯pool_recycle=-1 # 多久之后對線程池中的線程進行一次連接的回收（重置） )Base.metadata.create_all(engine)def drop_db():"""根據類刪除數據庫表:return: """engine = create_engine("mysql+pymysql://root:123@127.0.0.1:3306/s6?charset=utf8",max_overflow=0, # 超過連接池大小外最多創建的連接pool_size=5, # 連接池大小pool_timeout=30, # 池中沒有線程最多等待的時間，否則報錯pool_recycle=-1 # 多久之后對線程池中的線程進行一次連接的回收（重置） )Base.metadata.drop_all(engine)if __name__ == '__main__':drop_db()init_db()創建多個表并包含Fk、M2M關系創建多個表并包含Fk、M2M關系創建多個表并包含Fk、M2M關系

指定關聯列：hobby = relationship("Hobby", backref='pers',foreign_keys="Person.hobby_id")

b.操作數據庫表

#!/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)# 每次執行數據庫操作時，都需要創建一個session session = Session()# ############# 執行ORM操作 ############# obj1 = Users(name="alex1") session.add(obj1)# 提交事務 session.commit() # 關閉session session.close()

3.基于scoped_session實現線程安全

#!/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)""" # 線程安全，基于本地線程實現每個線程用同一個session # 特殊的：scoped_session中有原來方法的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)# ############# 執行ORM操作 ############# obj1 = Users(name="alex1") session.add(obj1)# 提交事務 session.commit() # 關閉session session.close()基于scoped_session實現線程安全基于scoped_session實現線程安全基于scoped_session實現線程安全

4.多線程執行示例

5.基本增刪改查示例

#!/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() """# ################ 刪除 ################ """ 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() """ # ################ 查詢 ################ """ 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()基本增刪改查示例基本增刪改查示例基本增刪改查示例

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. 默認條件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. 子查詢 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(上下聯合，去重) 和 union all(上下聯合，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.連表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語句

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='張三', hobby_id=3),Person(name='李四', hobby_id=4), ])person = Person(name='張九', hobby=Hobby(caption='姑娘')) session.add(person)hb = Hobby(caption='人妖') hb.pers = [Person(name='文飛'), Person(name='博雅')] session.add(hb)session.commit() """# 使用relationship正向查詢 """ v = session.query(Person).first() print(v.name) print(v.hobby.caption) """# 使用relationship反向查詢 """ 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組'),Group(name='B組'), ]) session.commit()s2g = Server2Group(server_id=1, group_id=1) session.add(s2g) session.commit()gp = Group(name='C組') 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組'),Group(name='G組')] session.add(ser) session.commit() """# 使用relationship正向查詢 """ v = session.query(Group).first() print(v.name) print(v.servers) """# 使用relationship反向查詢 """ 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

轉載于:https://www.cnblogs.com/tsboy/p/9210208.html

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