SQLAlchemy(3)
一. SQLAlchemy
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。
pip3 install sqlalchemy
流程图
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
使用
1. 执行原生SQL语句
举例1
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=, # 超过连接池大小外最多创建的连接
pool_size=, # 连接池大小
pool_timeout=, # 池中没有线程最多等待的时间,否则报错
pool_recycle=- # 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():
t = threading.Thread(target=task, args=(i,))
t.start()
举例2
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=, pool_size=) def task(arg):
conn = engine.contextual_connect()
with conn:
cur = conn.execute(
"select * from t1"
)
result = cur.fetchall()
print(result) for i in range():
t = threading.Thread(target=task, args=(i,))
t.start()
举例3
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=, pool_size=) def task(arg):
cur = engine.execute("select * from t1")
result = cur.fetchall()
cur.close()
print(result) for i in range():
t = threading.Thread(target=task, args=(i,))
t.start()
注意: 查看连接 show status like 'Threads%';
2. ORM
a. 创建数据库表
创建单表
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 </span>= Column(Integer, primary_key=<span style="color: #000000;">True)
name </span>= Column(String(<span style="color: #800080;">32</span>), index=True, nullable=<span style="color: #000000;">False)
# email </span>= Column(String(<span style="color: #800080;">32</span>), unique=<span style="color: #000000;">True)
# ctime </span>= Column(DateTime, <span style="color: #0000ff;">default</span>=<span style="color: #000000;">datetime.datetime.now)
# extra </span>= Column(Text, nullable=<span style="color: #000000;">True) __table_args__ </span>=<span style="color: #000000;"> (
# UniqueConstraint(</span><span style="color: #800000;">'</span><span style="color: #800000;">id</span><span style="color: #800000;">'</span>, <span style="color: #800000;">'</span><span style="color: #800000;">name</span><span style="color: #800000;">'</span>, name=<span style="color: #800000;">'</span><span style="color: #800000;">uix_id_name</span><span style="color: #800000;">'</span><span style="color: #000000;">),
# Index(</span><span style="color: #800000;">'</span><span style="color: #800000;">ix_id_name</span><span style="color: #800000;">'</span>, <span style="color: #800000;">'</span><span style="color: #800000;">name</span><span style="color: #800000;">'</span>, <span style="color: #800000;">'</span><span style="color: #800000;">email</span><span style="color: #800000;">'</span><span style="color: #000000;">),
)
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/s6?charset=utf8",
max_overflow=, # 超过连接池大小外最多创建的连接
pool_size=, # 连接池大小
pool_timeout=, # 池中没有线程最多等待的时间,否则报错
pool_recycle=- # 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/s6?charset=utf8",
max_overflow=, # 超过连接池大小外最多创建的连接
pool_size=, # 连接池大小
pool_timeout=, # 池中没有线程最多等待的时间,否则报错
pool_recycle=- # 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()创建单表
创建多个表并包含Fk、M2M关系
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()##################### 单表示例
class Users(Base):
tablename = 'users'id </span>= Column(Integer, primary_key=<span style="color: #000000;">True)
name </span>= Column(String(<span style="color: #800080;">32</span>), index=<span style="color: #000000;">True)
age </span>= Column(Integer, <span style="color: #0000ff;">default</span>=<span style="color: #800080;">18</span><span style="color: #000000;">)
email </span>= Column(String(<span style="color: #800080;">32</span>), unique=<span style="color: #000000;">True)
ctime </span>= Column(DateTime, <span style="color: #0000ff;">default</span>=<span style="color: #000000;">datetime.datetime.now)
extra </span>= Column(Text, nullable=<span style="color: #000000;">True) __table_args__ </span>=<span style="color: #000000;"> (
# UniqueConstraint(</span><span style="color: #800000;">'</span><span style="color: #800000;">id</span><span style="color: #800000;">'</span>, <span style="color: #800000;">'</span><span style="color: #800000;">name</span><span style="color: #800000;">'</span>, name=<span style="color: #800000;">'</span><span style="color: #800000;">uix_id_name</span><span style="color: #800000;">'</span><span style="color: #000000;">),
# Index(</span><span style="color: #800000;">'</span><span style="color: #800000;">ix_id_name</span><span style="color: #800000;">'</span>, <span style="color: #800000;">'</span><span style="color: #800000;">name</span><span style="color: #800000;">'</span>, <span style="color: #800000;">'</span><span style="color: #800000;">extra</span><span style="color: #800000;">'</span><span style="color: #000000;">),
)
class Hosts(Base):
tablename = 'hosts'id </span>= Column(Integer, primary_key=<span style="color: #000000;">True)
name </span>= Column(String(<span style="color: #800080;">32</span>), index=<span style="color: #000000;">True)
ctime </span>= Column(DateTime, <span style="color: #0000ff;">default</span>=<span style="color: #000000;">datetime.datetime.now)
##################### 一对多示例
class Hobby(Base):
tablename = 'hobby'
id = Column(Integer, primary_key=True)
caption = Column(String(), default='篮球')class Person(Base):
tablename = 'person'
nid = Column(Integer, primary_key=True)
name = Column(String(), index=True, nullable=True)
hobby_id = Column(Integer, ForeignKey("hobby.id"))# 与生成表结构无关,仅用于查询方便
hobby </span>= relationship(<span style="color: #800000;">"</span><span style="color: #800000;">Hobby</span><span style="color: #800000;">"</span>, backref=<span style="color: #800000;">'</span><span style="color: #800000;">pers</span><span style="color: #800000;">'</span><span style="color: #000000;">)
##################### 多对多示例
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(), unique=True, nullable=False)# 与生成表结构无关,仅用于查询方便
servers </span>= relationship(<span style="color: #800000;">'</span><span style="color: #800000;">Server</span><span style="color: #800000;">'</span>, secondary=<span style="color: #800000;">'</span><span style="color: #800000;">server2group</span><span style="color: #800000;">'</span>, backref=<span style="color: #800000;">'</span><span style="color: #800000;">groups</span><span style="color: #800000;">'</span><span style="color: #000000;">)
class Server(Base):
tablename = 'server'id </span>= Column(Integer, primary_key=True, autoincrement=<span style="color: #000000;">True)
hostname </span>= Column(String(<span style="color: #800080;">64</span>), unique=True, nullable=<span style="color: #000000;">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/s6?charset=utf8",
max_overflow=, # 超过连接池大小外最多创建的连接
pool_size=, # 连接池大小
pool_timeout=, # 池中没有线程最多等待的时间,否则报错
pool_recycle=- # 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/s6?charset=utf8",
max_overflow=, # 超过连接池大小外最多创建的连接
pool_size=, # 连接池大小
pool_timeout=, # 池中没有线程最多等待的时间,否则报错
pool_recycle=- # 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()创建多个表并包含Fk、M2M关系
指定关联列:hobby = relationship("Hobby", backref='pers',foreign_keys="Person.hobby_id")
b. 操作数据库表
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=, pool_size=)
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()
基于scoped_session实现线程安全
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=, pool_size=)
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
多线程执行示例
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=, pool_size=)
Session = sessionmaker(bind=engine) def task(arg):
session = Session()obj1 </span>= Users(name=<span style="color: #800000;">"</span><span style="color: #800000;">alex1</span><span style="color: #800000;">"</span><span style="color: #000000;">)
session.add(obj1) session.commit()
for i in range():
t = threading.Thread(target=task, args=(i,))
t.start()
基本增删改查示例
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=, pool_size=)
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()
"""################ 删除
"""
session.query(Users).filter(Users.id > ).delete()
session.commit()
"""
# ################ 修改 ################
"""
session.query(Users).filter(Users.id > ).update({"name" : ""})
session.query(Users).filter(Users.id > ).update({Users.name: Users.name + ""}, synchronize_session=False)
session.query(Users).filter(Users.id > ).update({"age": Users.age + }, synchronize_session="evaluate")
session.commit()
"""
# ################ 查询 ################
"""
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=, 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() 基本增删改查示例
常用操作
# 条件
ret = session.query(Users).filter_by(name='alex').all()
ret = session.query(Users).filter(Users.id > , Users.name == 'eric').all()
ret = session.query(Users).filter(Users.id.between(, ), Users.name == 'eric').all()
ret = session.query(Users).filter(Users.id.in_([,,])).all()
ret = session.query(Users).filter(~Users.id.in_([,,])).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 > , Users.name == 'eric')).all()
ret = session.query(Users).filter(or_(Users.id < , Users.name == 'eric')).all()
ret = session.query(Users).filter(
or_(
Users.id < ,
and_(Users.name == 'eric', Users.id > ),
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)[:]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()分组
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) >).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 > )
q2 = session.query(Favor.caption).filter(Favor.nid < )
ret = q1.union(q2).all() q1 = session.query(Users.name).filter(Users.id > )
q2 = session.query(Favor.caption).filter(Favor.nid < )
ret = q1.union_all(q2).all()
原生SQL语句
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=, pool_size=)
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":'wupeiqi'})
session.commit()
print(cursor.lastrowid) session.close() 原生SQL语句
基于relationship操作ForeignKey
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=, pool_size=)
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=),
Person(name='李四', hobby_id=),
]) 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) 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() 基于relationship操作ForeignKey
基于relationship操作m2m
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=, pool_size=)
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=, group_id=)
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m2m
其他
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=, pool_size=)
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)
"""
SELECTgroup
.name AS group_name, (SELECT count(server.id) AS sid
FROM server
WHERE server.id =group
.id) AS anon_1
FROMgroup
"""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()
本文参考链接:
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