SQLAlchemy基本使用(Flask中)
阿新 • • 發佈：2018-05-03
between -s rda msql apt 第三方插件 單表 idt odin 
SQLAlchemy介紹
SQLAlchemy是一個基於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，簡言之便是：將類和對象轉換成SQL，然後使用數據API執行SQL並獲取執行結果。
安裝:
pip3 install sqlalchemy
上圖組成部分：
- 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，其必依賴pymsql等第三方插件，Dialect用於和數據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-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...] 更多參考：http://docs.sqlalchemy.org/en/latest/dialects/index.html
基本使用
執行原生SQL語句
import timeimport threading import sqlalchemy from sqlalchemy import create_engine from sqlalchemy.engine.base import Engine engine = create_engine( "mysql+pymysql://root:[email protected]: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 # 多久之後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 Engine engine = create_engine("mysql+pymysql://root:[email protected]: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()示例1(接上↑)
#!/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:[email protected]: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()示例2（接上↑）
ORM
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 Base = 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(): """ 根據類創建數據庫表 :return: """ engine = create_engine( "mysql+pymysql://root:[email protected]: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 # 多久之後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:[email protected]: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 # 多久之後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() 創建單表創建單表
#!/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() # ##################### 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，僅用於查詢方便 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，僅用於查詢方便 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:[email protected]: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 # 多久之後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:[email protected]: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 # 多久之後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() 創建多個表並包含Fk、M2M關系創建多個表並包含Fk、Many2Many關系
指定關聯列：hobby = relationship("Hobby", backref=‘pers‘,foreign_keys="Person.hobby_id")
操作數據庫表
from sqlalchemy.orm import sessionmaker from sqlalchemy import create_engine from models import Users engine = create_engine("mysql+pymysql://root:[email protected]: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()基礎操作庫裏的表
#!/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:[email protected]: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() 多線程執行示例基於scoped_session實現線程安全
#!/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 sqlalchemy.sql import text from db import Users, Hosts engine = create_engine("mysql+pymysql://root:[email protected]: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
# 條件 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() # 分組 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() # 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() # 組合 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() 常用操作常用查詢操作
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:[email protected]:3306/s6", max_overflow=0, pool_size=5) Session = sessionmaker(bind=engine) session = Session() # 查詢 # 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實現
#!/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:[email protected]: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() 基於relationship操作ForeignKey基於relationship操作外鍵：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:[email protected]: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() 基於relationship操作m2m基於relationship操作多對多：Many2Many
關聯子查詢
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:[email protected]:3306/s6?charset=utf8", max_overflow=0, pool_size=5) Session = sessionmaker(bind=engine) session = Session() # 關聯子查詢 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 """ # 查詢 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()
SQLAlchemy基本使用(Flask中)