简介：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
Dialect用于和数据API进行交流，不同的数据库调用不同的api
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...]
基本操作：
1.链接数据库
1 import time 2 import threading 3 import sqlalchemy 4 from sqlalchemy import create_engine 5 from sqlalchemy.engine.base import Engine 6 #ok1为数据库名称 7 engine = create_engine( 8 "mysql+pymysql://root:123@localhost:3306/ok1?charset=utf8", 9 max_overflow=0, # 超过连接池大小外最多创建的连接 10 pool_size=5, # 连接池大小 11 pool_timeout=30, # 池中没有线程最多等待的时间，否则报错 12 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） 13 echo=True # 显示执行的所有SQL语句 14 )
取完数据自动关闭游标
1 #!/usr/bin/env python 2 # -*- coding:utf-8 -*- 3 import time 4 import threading 5 import sqlalchemy 6 from sqlalchemy import create_engine 7 from sqlalchemy.engine.base import Engine 8 9 engine = create_engine("mysql+pymysql://root:123@127.0.0.1:3306/t1", max_overflow=0, pool_size=5) 10 11 12 def task(arg): 13 conn = engine.contextual_connect() 14 with conn: 15 cur = conn.execute( 16 "select * from t1" 17 ) 18 result = cur.fetchall() 19 print(result) 20 21 22 for i in range(20): 23 t = threading.Thread(target=task, args=(i,)) 24 t.start()
2. 执行原生sql语句
1 import time 2 import threading 3 import sqlalchemy 4 from sqlalchemy import create_engine 5 from sqlalchemy.engine.base import Engine 6 7 engine = create_engine( 8 "mysql+pymysql://root:123@127.0.0.1:3306/t1?charset=utf8", 9 max_overflow=0, # 超过连接池大小外最多创建的连接 10 pool_size=5, # 连接池大小 11 pool_timeout=30, # 池中没有线程最多等待的时间，否则报错 12 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） 13 ) 14 15 16 def task(arg): 17 conn = engine.raw_connection() 18 cursor = conn.cursor() 19 cursor.execute( 20 "select * from book" 21 ) 22 result = cursor.fetchall() 23 cursor.close() 24 conn.close() 25 26 27 for i in range(10): 28 t = threading.Thread(target=task, args=(i,)) 29 t.start()
1 #!/usr/bin/env python 2 # -*- coding:utf-8 -*- 3 import time 4 import threading 5 import sqlalchemy 6 from sqlalchemy import create_engine 7 from sqlalchemy.engine.base import Engine 8 from sqlalchemy.engine.result import ResultProxy 9 engine = create_engine("mysql+pymysql://root:123@127.0.0.1:3306/t1", max_overflow=0, pool_size=5) 10 11 12 def task(arg): 13 cur = engine.execute("select * from t1") 14 result = cur.fetchall() 15 cur.close() 16 print(result) 17 18 19 for i in range(20): 20 t = threading.Thread(target=task, args=(i,)) 21 t.start()
3.ORM使用
a.表的创建
1 #!/usr/bin/env python 2 # -*- coding:utf-8 -*- 3 import datetime 4 from sqlalchemy import create_engine 5 from sqlalchemy.ext.declarative import declarative_base 6 from sqlalchemy import Column, Integer, String, Text, ForeignKey, DateTime, UniqueConstraint, Index 7 8 Base = declarative_base() 9 10 11 class Users(Base): 12 __tablename__ = ‘users‘ 13 14 id = Column(Integer, primary_key=True) 15 name = Column(String(32), index=True, nullable=False) 16 # email = Column(String(32), unique=True) 17 # ctime = Column(DateTime, default=datetime.datetime.now) 18 # extra = Column(Text, nullable=True) 19 20 __table_args__ = ( 21 # UniqueConstraint(‘id‘, ‘name‘, name=‘uix_id_name‘), 22 # Index(‘ix_id_name‘, ‘name‘, ‘email‘), 23 ) 24 25 26 def init_db(): 27 """ 28 根据类创建数据库表 29 :return: 30 """ 31 engine = create_engine( 32 "mysql+pymysql://root:123@127.0.0.1:3306/s6?charset=utf8", 33 max_overflow=0, # 超过连接池大小外最多创建的连接 34 pool_size=5, # 连接池大小 35 pool_timeout=30, # 池中没有线程最多等待的时间，否则报错 36 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） 37 ) 38 39 Base.metadata.create_all(engine) 40 41 42 def drop_db(): 43 """ 44 根据类删除数据库表 45 :return: 46 """ 47 engine = create_engine( 48 "mysql+pymysql://root:123@127.0.0.1:3306/s6?charset=utf8", 49 max_overflow=0, # 超过连接池大小外最多创建的连接 50 pool_size=5, # 连接池大小 51 pool_timeout=30, # 池中没有线程最多等待的时间，否则报错 52 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） 53 ) 54 55 Base.metadata.drop_all(engine) 56 57 if __name__ == ‘__main__‘: 58 drop_db() 59 init_db() 60 61 创建单表
1 #!/usr/bin/env python 2 # -*- coding:utf-8 -*- 3 import datetime 4 from sqlalchemy import create_engine 5 from sqlalchemy.ext.declarative import declarative_base 6 from sqlalchemy import Column, Integer, String, Text, ForeignKey, DateTime, UniqueConstraint, Index 7 from sqlalchemy.orm import relationship 8 9 Base = declarative_base() 10 11 12 # ##################### 单表示例 ######################### 13 class Users(Base): 14 __tablename__ = ‘users‘ 15 16 id = Column(Integer, primary_key=True) 17 name = Column(String(32), index=True) 18 age = Column(Integer, default=18) 19 email = Column(String(32), unique=True) 20 ctime = Column(DateTime, default=datetime.datetime.now) 21 extra = Column(Text, nullable=True) 22 23 __table_args__ = ( 24 # UniqueConstraint(‘id‘, ‘name‘, name=‘uix_id_name‘), 25 # Index(‘ix_id_name‘, ‘name‘, ‘extra‘), 26 ) 27 28 29 class Hosts(Base): 30 __tablename__ = ‘hosts‘ 31 32 id = Column(Integer, primary_key=True) 33 name = Column(String(32), index=True) 34 ctime = Column(DateTime, default=datetime.datetime.now) 35 36 37 # ##################### 一对多示例 ######################### 38 class Hobby(Base): 39 __tablename__ = ‘hobby‘ 40 id = Column(Integer, primary_key=True) 41 caption = Column(String(50), default=‘篮球‘) 42 43 44 class Person(Base): 45 __tablename__ = ‘person‘ 46 nid = Column(Integer, primary_key=True) 47 name = Column(String(32), index=True, nullable=True) 48 hobby_id = Column(Integer, ForeignKey("hobby.id")) 49 50 # 与生成表结构无关，仅用于查询方便 51 hobby = relationship("Hobby", backref=‘pers‘) 52 53 54 # ##################### 多对多示例 ######################### 55 56 class Server2Group(Base): 57 __tablename__ = ‘server2group‘ 58 id = Column(Integer, primary_key=True, autoincrement=True) 59 server_id = Column(Integer, ForeignKey(‘server.id‘)) 60 group_id = Column(Integer, ForeignKey(‘group.id‘)) 61 62 63 class Group(Base): 64 __tablename__ = ‘group‘ 65 id = Column(Integer, primary_key=True) 66 name = Column(String(64), unique=True, nullable=False) 67 68 # 与生成表结构无关，仅用于查询方便 69 servers = relationship(‘Server‘, secondary=‘server2group‘, backref=‘groups‘) 70 71 72 class Server(Base): 73 __tablename__ = ‘server‘ 74 75 id = Column(Integer, primary_key=True, autoincrement=True) 76 hostname = Column(String(64), unique=True, nullable=False) 77 78 79 def init_db(): 80 """ 81 根据类创建数据库表 82 :return: 83 """ 84 engine = create_engine( 85 "mysql+pymysql://root:123@127.0.0.1:3306/s6?charset=utf8", 86 max_overflow=0, # 超过连接池大小外最多创建的连接 87 pool_size=5, # 连接池大小 88 pool_timeout=30, # 池中没有线程最多等待的时间，否则报错 89 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） 90 ) 91 92 Base.metadata.create_all(engine) 93 94 95 def drop_db(): 96 """ 97 根据类删除数据库表 98 :return: 99 """ 100 engine = create_engine( 101 "mysql+pymysql://root:123@127.0.0.1:3306/s6?charset=utf8", 102 max_overflow=0, # 超过连接池大小外最多创建的连接 103 pool_size=5, # 连接池大小 104 pool_timeout=30, # 池中没有线程最多等待的时间，否则报错 105 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） 106 ) 107 108 Base.metadata.drop_all(engine) 109 110 111 if __name__ == ‘__main__‘: 112 drop_db() 113 init_db() 114 115 创建多个表并包含Fk、M2M关系
b.数据库的操作
1 from sqlalchemy.orm import sessionmaker 2 from sqlalchemy import create_engine 3 from models import Users,Person,Hobby 4 engine = create_engine( 5 "mysql+pymysql://root:123@localhost:3306/ok1?charset=utf8", 6 max_overflow=0, # 超过连接池大小外最多创建的连接 7 pool_size=5, # 连接池大小 8 pool_timeout=30, # 池中没有线程最多等待的时间，否则报错 9 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） 10 ) 11 Session = sessionmaker(bind=engine) 12 # 每次执行数据库操作时，都需要创建一个session，申请一个连接 13 session = Session() 14 # ############# 执行ORM操作 ############# 15 # obj1 = Users(name="xxx") 16 # obj2 = Users(name="yyy") 17 # session.add(obj1) 18 # session.add(obj2) 19 # 增加多个项目，用add_all 20 # session.add_all([ 21 # Users(name="aaa"), 22 # Users(name="bbb") 23 # ]) 24 # 提交事务 25 # session.commit() 26 from sqlalchemy import and_, or_ 27 ret = session.query(Person).join(Hobby,Person.hobby_id==Hobby.id,isouter=True) 28 # ret = session.query(Person).join(Hobby,and_(Person.hobby_id==Hobby.id,Person.id >2),isouter=True) 29 print(ret) 30 # 关闭session 31 session.close()
1 #!/usr/bin/env python 2 # -*- coding:utf-8 -*- 3 import time 4 import threading 5 6 from sqlalchemy.ext.declarative import declarative_base 7 from sqlalchemy import Column, Integer, String, ForeignKey, UniqueConstraint, Index 8 from sqlalchemy.orm import sessionmaker, relationship 9 from sqlalchemy import create_engine 10 from db import Users 11 12 engine = create_engine("mysql+pymysql://root:123@127.0.0.1:3306/s6", max_overflow=0, pool_size=5) 13 Session = sessionmaker(bind=engine) 14 15 16 def task(arg): 17 session = Session() 18 19 obj1 = Users(name="alex1") 20 session.add(obj1) 21 22 session.commit() 23 24 25 for i in range(10): 26 t = threading.Thread(target=task, args=(i,)) 27 t.start() 28 29 多线程执行示例
1 #!/usr/bin/env python 2 # -*- coding:utf-8 -*- 3 import time 4 import threading 5 6 from sqlalchemy.ext.declarative import declarative_base 7 from sqlalchemy import Column, Integer, String, ForeignKey, UniqueConstraint, Index 8 from sqlalchemy.orm import sessionmaker, relationship 9 from sqlalchemy import create_engine 10 from sqlalchemy.sql import text 11 12 from db import Users, Hosts 13 14 engine = create_engine("mysql+pymysql://root:123@127.0.0.1:3306/s6", max_overflow=0, pool_size=5) 15 Session = sessionmaker(bind=engine) 16 17 session = Session() 18 19 # ################ 添加 ################ 20 """ 21 obj1 = Users(name="wupeiqi") 22 session.add(obj1) 23 24 session.add_all([ 25 Users(name="wupeiqi"), 26 Users(name="alex"), 27 Hosts(name="c1.com"), 28 ]) 29 session.commit() 30 """ 31 32 # ################ 删除 ################ 33 """ 34 session.query(Users).filter(Users.id > 2).delete() 35 session.commit() 36 """ 37 # ################ 修改 ################ 38 """ 39 session.query(Users).filter(Users.id > 0).update({"name" : "099"}) 40 session.query(Users).filter(Users.id > 0).update({Users.name: Users.name + "099"}, synchronize_session=False) 41 session.query(Users).filter(Users.id > 0).update({"age": Users.age + 1}, synchronize_session="evaluate") 42 session.commit() 43 """ 44 # ################ 查询 ################ 45 """ 46 r1 = session.query(Users).all() 47 r2 = session.query(Users.name.label(‘xx‘), Users.age).all() 48 r3 = session.query(Users).filter(Users.name == "alex").all() 49 r4 = session.query(Users).filter_by(name=‘alex‘).all() 50 r5 = session.query(Users).filter_by(name=‘alex‘).first() 51 r6 = session.query(Users).filter(text("id""" 52 53 54 session.close() 55 56 基本增删改查示例
ps：sqlalchemy session 执行 delete 时 synchronize_session 策略
1 False 2 不同步 session，如果被删除的 objects 已经在 session 中存在，在 session commit 或者 expire_all 之前，这些被删除的对象都存在 session 中。 3 4 不同步可能会导致获取被删除 objects 时出错。 5 6 fatch 7 删除之前从 db 中匹配被删除的对象并保存在 session 中，然后再从 session 中删除，这样做是为了让 session 的对象管理 identity_map 得知被删除的对象究竟是哪些以便更新引用关系。 8 9 evaluate 10 默认值。根据当前的 query criteria 扫描 session 中的 objects，如果不能正确执行则抛出错误，这句话也可以理解为，如果 session 中原本就没有这些被删除的 objects，扫描当然不会发生匹配，相当于匹配未正确执行。 11 12 注意这里报错只会在特定 query criteria 时报错，比如 in 操作。
1 # 条件 2 ret = session.query(Users).filter_by(name=‘alex‘).all() 3 ret = session.query(Users).filter(Users.id > 1, Users.name == ‘eric‘).all() 4 ret = session.query(Users).filter(Users.id.between(1, 3), Users.name == ‘eric‘).all() 5 ret = session.query(Users).filter(Users.id.in_([1,3,4])).all() 6 ret = session.query(Users).filter(~Users.id.in_([1,3,4])).all() 7 ret = session.query(Users).filter(Users.id.in_(session.query(Users.id).filter_by(name=‘eric‘))).all() 8 from sqlalchemy import and_, or_ 9 ret = session.query(Users).filter(and_(Users.id > 3, Users.name == ‘eric‘)).all() 10 ret = session.query(Users).filter(or_(Users.id < 2, Users.name == ‘eric‘)).all() 11 ret = session.query(Users).filter( 12 or_( 13 Users.id < 2, 14 and_(Users.name == ‘eric‘, Users.id > 3), 15 Users.extra != "" 16 )).all() 17 18 19 # 通配符 20 ret = session.query(Users).filter(Users.name.like(‘e%‘)).all() 21 ret = session.query(Users).filter(~Users.name.like(‘e%‘)).all() 22 23 # 限制 24 ret = session.query(Users)[1:2] 25 26 # 排序 27 ret = session.query(Users).order_by(Users.name.desc()).all() 28 ret = session.query(Users).order_by(Users.name.desc(), Users.id.asc()).all() 29 30 # 分组 31 from sqlalchemy.sql import func 32 33 ret = session.query(Users).group_by(Users.extra).all() 34 ret = session.query( 35 func.max(Users.id), 36 func.sum(Users.id), 37 func.min(Users.id)).group_by(Users.name).all() 38 39 ret = session.query( 40 func.max(Users.id), 41 func.sum(Users.id), 42 func.min(Users.id)).group_by(Users.name).having(func.min(Users.id) >2).all() 43 44 # 连表 45 46 ret = session.query(Users, Favor).filter(Users.id == Favor.nid).all() 47 48 ret = session.query(Person).join(Favor).all() 49 50 ret = session.query(Person).join(Favor, isouter=True).all() 51 52 53 # 组合 54 q1 = session.query(Users.name).filter(Users.id > 2) 55 q2 = session.query(Favor.caption).filter(Favor.nid < 2) 56 ret = q1.union(q2).all() 57 58 q1 = session.query(Users.name).filter(Users.id > 2) 59 q2 = session.query(Favor.caption).filter(Favor.nid < 2) 60 ret = q1.union_all(q2).all() 61 62 常用操作
1 #!/usr/bin/env python 2 # -*- coding:utf-8 -*- 3 import time 4 import threading 5 6 from sqlalchemy.ext.declarative import declarative_base 7 from sqlalchemy import Column, Integer, String, ForeignKey, UniqueConstraint, Index 8 from sqlalchemy.orm import sessionmaker, relationship 9 from sqlalchemy import create_engine 10 from sqlalchemy.sql import text 11 from sqlalchemy.engine.result import ResultProxy 12 from db import Users, Hosts 13 14 engine = create_engine("mysql+pymysql://root:123@127.0.0.1:3306/s6", max_overflow=0, pool_size=5) 15 Session = sessionmaker(bind=engine) 16 17 session = Session() 18 19 # 查询 20 # cursor = session.execute(‘select * from users‘) 21 # result = cursor.fetchall() 22 23 # 添加 24 cursor = session.execute(‘insert into users(name) values(:value)‘,params={"value":‘wupeiqi‘}) 25 session.commit() 26 print(cursor.lastrowid) 27 28 session.close() 29 30 原生SQL语句
1 #!/usr/bin/env python 2 # -*- coding:utf-8 -*- 3 import time 4 import threading 5 6 from sqlalchemy.ext.declarative import declarative_base 7 from sqlalchemy import Column, Integer, String, ForeignKey, UniqueConstraint, Index 8 from sqlalchemy.orm import sessionmaker, relationship 9 from sqlalchemy import create_engine 10 from sqlalchemy.sql import text 11 from sqlalchemy.engine.result import ResultProxy 12 from db import Users, Hosts, Hobby, Person 13 14 engine = create_engine("mysql+pymysql://root:123@127.0.0.1:3306/s6?charset=utf8", max_overflow=0, pool_size=5) 15 Session = sessionmaker(bind=engine) 16 session = Session() 17 # 添加 18 """ 19 session.add_all([ 20 Hobby(caption=‘乒乓球‘), 21 Hobby(caption=‘羽毛球‘), 22 Person(name=‘张三‘, hobby_id=3), 23 Person(name=‘李四‘, hobby_id=4), 24 ]) 25 26 person = Person(name=‘张九‘, hobby=Hobby(caption=‘姑娘‘)) 27 session.add(person) 28 29 hb = Hobby(caption=‘人妖‘) 30 hb.pers = [Person(name=‘文飞‘), Person(name=‘博雅‘)] 31 session.add(hb) 32 33 session.commit() 34 """ 35 36 # 使用relationship正向查询 37 """ 38 v = session.query(Person).first() 39 print(v.name) 40 print(v.hobby.caption) 41 """ 42 43 # 使用relationship反向查询 44 """ 45 v = session.query(Hobby).first() 46 print(v.caption) 47 print(v.pers) 48 """ 49 50 session.close() 51 52 基于relationship操作ForeignKey
1 #!/usr/bin/env python 2 # -*- coding:utf-8 -*- 3 import time 4 import threading 5 6 from sqlalchemy.ext.declarative import declarative_base 7 from sqlalchemy import Column, Integer, String, ForeignKey, UniqueConstraint, Index 8 from sqlalchemy.orm import sessionmaker, relationship 9 from sqlalchemy import create_engine 10 from sqlalchemy.sql import text 11 from sqlalchemy.engine.result import ResultProxy 12 from db import Users, Hosts, Hobby, Person, Group, Server, Server2Group 13 14 engine = create_engine("mysql+pymysql://root:123@127.0.0.1:3306/s6?charset=utf8", max_overflow=0, pool_size=5) 15 Session = sessionmaker(bind=engine) 16 session = Session() 17 # 添加 18 """ 19 session.add_all([ 20 Server(hostname=‘c1.com‘), 21 Server(hostname=‘c2.com‘), 22 Group(name=‘A组‘), 23 Group(name=‘B组‘), 24 ]) 25 session.commit() 26 27 s2g = Server2Group(server_id=1, group_id=1) 28 session.add(s2g) 29 session.commit() 30 31 32 gp = Group(name=‘C组‘) 33 gp.servers = [Server(hostname=‘c3.com‘),Server(hostname=‘c4.com‘)] 34 session.add(gp) 35 session.commit() 36 37 38 ser = Server(hostname=‘c6.com‘) 39 ser.groups = [Group(name=‘F组‘),Group(name=‘G组‘)] 40 session.add(ser) 41 session.commit() 42 """ 43 44 45 # 使用relationship正向查询 46 """ 47 v = session.query(Group).first() 48 print(v.name) 49 print(v.servers) 50 """ 51 52 # 使用relationship反向查询 53 """ 54 v = session.query(Server).first() 55 print(v.hostname) 56 print(v.groups) 57 """ 58 59 60 session.close() 61 62 基于relationship操作m2m
1 #!/usr/bin/env python 2 # -*- coding:utf-8 -*- 3 import time 4 import threading 5 6 from sqlalchemy.ext.declarative import declarative_base 7 from sqlalchemy import Column, Integer, String, ForeignKey, UniqueConstraint, Index 8 from sqlalchemy.orm import sessionmaker, relationship 9 from sqlalchemy import create_engine 10 from sqlalchemy.sql import text, func 11 from sqlalchemy.engine.result import ResultProxy 12 from db import Users, Hosts, Hobby, Person, Group, Server, Server2Group 13 14 engine = create_engine("mysql+pymysql://root:123@127.0.0.1:3306/s6?charset=utf8", max_overflow=0, pool_size=5) 15 Session = sessionmaker(bind=engine) 16 session = Session() 17 18 # 关联子查询 19 subqry = session.query(func.count(Server.id).label("sid")).filter(Server.id == Group.id).correlate(Group).as_scalar() 20 result = session.query(Group.name, subqry) 21 """ 22 SELECT `group`.name AS group_name, (SELECT count(server.id) AS sid 23 FROM server 24 WHERE server.id = `group`.id) AS anon_1 25 FROM `group` 26 """ 27 28 29 # 原生SQL 30 """ 31 # 查询 32 cursor = session.execute(‘select * from users‘) 33 result = cursor.fetchall() 34 35 # 添加 36 cursor = session.execute(‘insert into users(name) values(:value)‘,params={"value":‘wupeiqi‘}) 37 session.commit() 38 print(cursor.lastrowid) 39 """ 40 41 session.close() 42 43 其他
