时间：2021-07-01 10:21:17 帮助过：13人阅读
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pip3 install sqlalchemy
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组成部分：
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：
SQLAlchemy用一个字符串表示连接信息：
‘数据库类型+数据库驱动名称://用户名:口令@机器地址:端口号/数据库名‘
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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：http://docs.sqlalchemy.org/en/latest/dialects/index.html
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import time
import threading
import sqlalchemy
from sqlalchemy import create_engine
from sqlalchemy.engine.base import Engine
engine = 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, # 池中没有线程时，最多等待的时间，超时报错，默认30秒
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），-1代表永远不回收，即一直被重用
)
def task(arg):
conn = engine.raw_connection() #拿到的是一个原生的pymysql连接对象
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: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，进程cmd，mysql中>输入 show status like ‘Threads%‘;
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() # 创建对象的基类:
# 定义User对象:
class Users(Base):
# 表的名字:
__tablename__ = ‘users‘
# 表的结构:
id = Column(Integer, primary_key=True)
name = Column(String(32), index=True, nullable=False,default=‘xx‘) # index指定是否是索引，nullable是否能为空
email = Column(String(32), unique=True) # 指定唯一
ctime = Column(DateTime, default=datetime.datetime.now) #注意，此处设置时datetime.datetime.now若加了括号，则时间永远是程序启动时的时间，后面创建数据时，不会变化
extra = Column(Text, nullable=True)
__table_args__ = (
UniqueConstraint(‘id‘, ‘name‘, name=‘uix_id_name‘), # 联合唯一索引
Index(‘ix_id_name‘, ‘name‘, ‘email‘), #给name和email创建普通索引，索引名为ix_id_name
)
def init_db():
"""
根据类创建数据库表
:return:
"""
# 初始化数据库连接:
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) #找到所有继承了Base的类，按照其结构建表
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()
默认建的表的引擎是MyISAM，如果要设置成InnoDB（支持事务），该怎么设置呢？
__table_args__ = { ‘mysql_engine‘: ‘InnoDB‘, # 指定表的引擎 ‘mysql_charset‘: ‘utf8‘ # 指定表的编码格式 }
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() # 创建对象的基类:
# ##################### 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")) #建FK关系
# 与生成表结构无关，仅用于查询方便
hobby = relationship("Hobby", backref=‘pers‘) #反向关联的名字
# ##################### 多对多示例 #########################
# 这里多对多需要自己建第三张表，并绑定关系
class Server2Group(Base):
__tablename__ = ‘server2group‘
id = Column(Integer, primary_key=True, autoincrement=True) #autoincrement 设置自增
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‘) #反向关联的名字
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/userinfo?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/userinfo?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()
SQLALchemy不同于Django的ORM，当创建多对多关联事，不会自动创建第三张表，需要我们自己定义关系表，进行关联
#!/usr/bin/env python
# -*- coding:utf-8 -*-
from sqlalchemy.orm import sessionmaker
from sqlalchemy import create_engine
from models import Users
engine = create_engine("mysql+pymysql://root:123@127.0.0.1:3306/s6", max_overflow=0, pool_size=5)
Session = sessionmaker(bind=engine) #创建Session类
# 每次执行数据库操作时，都需要创建一个session
session = Session() # 创建session对象:
# ############# 执行ORM操作 #############
# 创建新User对象
obj1 = Users(name="alex1")
# 添加到session:
session.add(obj1)
# 提交即保存到数据库:
session.commit()
# 关闭session
session.close()
#!/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 engine = 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":‘hc‘}) # 注意占位符和传参的形式 session.commit() print(cursor.lastrowid) session.close() 原生SQL语句View Code
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:123@127.0.0.1:3306/s6", max_overflow=0, pool_size=5)
Session = sessionmaker(bind=engine)
session = Session()
# ################ 添加 ################
obj1 = Users(name="hc")
session.add(obj1) #添加一个对象
session.add_all([
Users(name="hc"),
Users(name="alex"),
Hosts(name="c1.com"),
]) #添加多个对象
session.commit()
# ################ 删除 ################
# filter是where条件，最后调用one()或first()返回唯一行，如果调用all()则返回所有行
session.query(Users).filter(Users.id > 2).delete() #删除Users表中id大于2的数据
session.commit()
# ################ 修改 ################
session.query(Users).filter(Users.id > 0).update({"name" : "099"}) # 将Users表中id>0的数据，把name字段改为099
session.query(Users).filter(Users.id > 0).update({Users.name: Users.name + "099"}, synchronize_session=False)
#synchronize_session设置为False即执行字符串拼接
session.query(Users).filter(Users.id > 0).update({"age": Users.age + 1}, synchronize_session="evaluate")
#synchronize_session设置为evaluate即执行四则运算
session.commit()
# ################ 查询 ################
r1 = session.query(Users).all()
r2 = session.query(Users.name.label(‘xx‘), Users.age).all() #label 取别名的，即在查询结果中，显示name的别名‘xx‘
r3 = session.query(Users).filter(Users.name == "alex").one() # one()返回唯一行,类似于django的get,如果返回数据为多个则报错
r3 = session.query(Users).filter(Users.name == "alex").all() # all()获取所有数据
r4 = session.query(Users).filter_by(name=‘alex‘).all() # 注意filter和filter_by后面括号内条件的写法
r5 = session.query(Users).filter_by(name=‘alex‘).first() # first()获取返回数据的第一行
r6 = session.query(Users).filter(text("id<:value and name=:name")).params(value=224, name=‘fred‘).order_by(Users.id).all()
#order_by后面还可以.desc()降序排列，默认为.asc()升序排列
# text(自定义条件，:的功能类似%s占位)，params中进行传参
r7 = session.query(Users).from_statement(text("SELECT * FROM Hosts where name=:name")).params(name=‘ed‘).all()
# text中还能从另一个表中查询，前面要用from_statement，而不是filter
session.close()
#!/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: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) # 会同时创建3条数据(1条hobby的数据，2条person的数据)
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()
#!/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: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m2mView Code
and、or、like、limit、排序、分组、连表、组合
# 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_ #需要导入 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() # 倒序排列 ret = session.query(Users).order_by(Users.name.desc(), Users.id.asc()).all() # 分组 from sqlalchemy.sql import func #需要导入 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() # 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()View Code
关联子查询
#!/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, func from sqlalchemy.engine.result import ResultProxy from db import Users, Hosts, Hobby, Person, Group, Server, Server2Group engine = 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()View Code
子查询： session.query(Users).filter(Users.id.in_(session.query(Users.id).filter_by(name=‘eric‘))).all() """ select * from users where id in (select id from xxx) """ subqry = session.query(func.count(Server.id).label("sid")).filter(Server.id == Group.id).correlate(Group).as_scalar() #第一步： session.query(func.count(Server.id).label("sid")).filter(Server.id == Group.id) #这句的sql语句为 select count(id) as sid from server where server.id = group.id 如果直接运行，则会报错 # 第二步：.correlate(Group).as_scalar() ==> 代表此时不执行查询操作，将其当作条件，在group表中查询时，才执行查询 result = session.query(Group.name, subqry) # sql语句为：select group.name subqry from group #第三步：将subqry替换为上面的条件，则此句的SQL为： # select group.name,(select count(id) as sid from server where server.id = group.id) as xx from group
点击
#!/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 Users engine = 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
#!/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: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
SqlAlchemy本身没有chocie,需要安装这个才能提供choice功能
pip install sqlalchemy-utils
from sqlalchemy.ext.declarative import declarative_base from sqlalchemy import Column,Integer,String from sqlalchemy_utils import ChoiceType from sqlalchemy import create_engine Base = declarative_base() class User(Base): __tablename__ = ‘users‘ type_choices=( (1,‘北京‘), (2,‘上海‘), ) id = Column(Integer, primary_key=True) #必须要有主键 name =Column(String(64)) types=Column(ChoiceType(type_choices,Integer())) # 注意：Integer后面要有括号 __table_args__ = { ‘mysql_engine‘: ‘InnoDB‘, ‘mysql_charset‘: ‘utf8‘ } 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/db1?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/db1?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()建表
#! /usr/bin/env python # -*- coding: utf-8 -*- # __author__ = "HuChong" # Date: 2018/1/12 from sqlalchemy.orm import sessionmaker from sqlalchemy import create_engine from ru import User engine = create_engine("mysql+pymysql://root:123@127.0.0.1:3306/db1", max_overflow=0, pool_size=5) Session = sessionmaker(bind=engine) session = Session() obj1 = User(name="xz",types=1) obj2 = User(name="zz",types=2) session.add_all([obj1,obj2]) session.commit() session.close()插入数据
#! /usr/bin/env python # -*- coding: utf-8 -*- # __author__ = "HuChong" # Date: 2018/1/12 from sqlalchemy.orm import sessionmaker from sqlalchemy import create_engine from ru import User engine = create_engine("mysql+pymysql://root:123@127.0.0.1:3306/db1", max_overflow=0, pool_size=5) Session = sessionmaker(bind=engine) session = Session() result_list=session.query(User).all() print(result_list) for item in result_list: print(item.types) print(item.types.code,item.types.value) session.close() #######打印结果如下######## ‘‘‘ [<ru.User object at 0x0386D770>, <ru.User object at 0x0386D7D0>] Choice(code=1, value=北京) 1 北京 Choice(code=2, value=上海) 2 上海 ‘‘‘获取值
Flask-SQLAlchemy
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