SQLAlchemy的使用(SQLAlchemy 是一种对象关系映射模型(Object Relational Mapper), 简称ORM。)

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。

pip install sqlalchemy -i http://pypi.douban.com/simple --trusted-host pypi.douban.com

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-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

二. 使用

1. 执行原生SQL语句

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()

 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()

 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()

注意: 查看连接 show status like 'Threads%';

2. ORM

a. 创建数据库表

 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 
 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 
58 if __name__ == '__main__':
59     drop_db()
60     init_db()

  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()

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 Users
 
engine = create_engine("mysql+pymysql://root:123@127.0.0.1:3306/s6", max_overflow=0, pool_size=5)
##############方式一########################
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()

######################方式二####################

# 方式二：支持线程安全，为每个线程创建一个session
# - threading.Local
# - 唯一标识
# ScopedSession对象
# self.registry(), 加括号创建session
# self.registry(), 加括号创建session
# self.registry(), 加括号创建session
from greenlet import getcurrent as get_ident

Session = sessionmaker(bind=engine)

session = scoped_session(Session,get_ident)
# session.add
# 操作
session.remove()

 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()

 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<:value and name=:name")).params(value=224, name='fred').order_by(Users.id).all()
52 r7 = session.query(Users).from_statement(text("SELECT * FROM users where name=:name")).params(name='ed').all()
53 """
54 
55 
56 session.close()

 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()

 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()

 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()

 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()

 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()

基本增删改查补充

#!/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: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)

#批量添加
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) #字符串
session.query(Users).filter(Users.id > 0).update({"age": Users.age + 1}, synchronize_session="evaluate")  #数字
session.commit()
"""
# ################ 查询 ################
"""
r1 = session.query(Users).all()
r2 = session.query(Users.name.label('xx'), Users.age).all()   #lable #as xx
r3 = session.query(Users).filter(Users.name == "alex").all()
r4 = session.query(Users).filter_by(name='alex').all()   #如果里面写条件就用filter_by,和上面filter查询是一回事，只是一种不同的方式
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()  #查询里面如果有动态传参的时候，吧它包在text里面，:value,:name这样的语法后面用.params来进行格式化
r7 = session.query(Users).from_statement(text("SELECT * FROM users where name=:name")).params(name='ed').all()  #上面的这个方式也可以用这一种 ，直接可以进行SQL语句的查询
"""


session.close()