SQLAlchemy 進階

SQLAlchemy使用

一、執行原生SQL語句

from sqlalchemy.orm import sessionmaker
from sqlalchemy import create_engine
from sqlalchemy.orm import scoped_session
from models import Student,Course,Student2Course

engine = create_engine(
		"mysql+pymysql://root:123456@127.0.0.1:3306/s9day120?charset=utf8",
		max_overflow=0,  # 超過鏈接池大小外最多建立的鏈接
		pool_size=5,  # 鏈接池大小
		pool_timeout=30,  # 池中沒有線程最多等待的時間，不然報錯
		pool_recycle=-1  # 多久以後對線程池中的線程進行一次鏈接的回收（重置）
	)
SessionFactory = sessionmaker(bind=engine)
session = scoped_session(SessionFactory)


def task():
	""""""
	# 方式一：
	"""
	# 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)
	"""
	# 方式二：
	"""
	# conn = engine.raw_connection()
	# cursor = conn.cursor()
	# cursor.execute(
	#     "select * from t1"
	# )
	# result = cursor.fetchall()
	# cursor.close()
	# conn.close()
	"""

	# 將鏈接交還給鏈接池
	session.remove()


from threading import Thread

for i in range(20):
	t = Thread(target=task)
	t.start()

二、建立數據庫表

#!/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
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():
    """
    根據類建立數據庫表
    :return: 
    """
    engine = create_engine(
        "mysql+pymysql://root:123@127.0.0.1:3306/s6?charset=utf8",
        max_overflow=0,  # 超過鏈接池大小外最多建立的鏈接
        pool_size=5,  # 鏈接池大小
        pool_timeout=30,  # 池中沒有線程最多等待的時間，不然報錯
        pool_recycle=-1  # 多久以後對線程池中的線程進行一次鏈接的回收（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:123@127.0.0.1:3306/s6?charset=utf8",
        max_overflow=0,  # 超過鏈接池大小外最多建立的鏈接
        pool_size=5,  # 鏈接池大小
        pool_timeout=30,  # 池中沒有線程最多等待的時間，不然報錯
        pool_recycle=-1  # 多久以後對線程池中的線程進行一次鏈接的回收（重置）
    )

    Base.metadata.drop_all(engine)


if __name__ == '__main__':
    drop_db()
    init_db()

 　

方式一：
from sqlalchemy.orm import sessionmaker
from sqlalchemy import create_engine
from models import Student,Course,Student2Course

engine = create_engine(
        "mysql+pymysql://root:123456@127.0.0.1:3306/s9day120?charset=utf8",
        max_overflow=0,  # 超過鏈接池大小外最多建立的鏈接
        pool_size=5,  # 鏈接池大小
        pool_timeout=30,  # 池中沒有線程最多等待的時間，不然報錯
        pool_recycle=-1  # 多久以後對線程池中的線程進行一次鏈接的回收（重置）
    )
SessionFactory = sessionmaker(bind=engine)

def task():
    # 去鏈接池中獲取一個鏈接
    session = SessionFactory()

    ret = session.query(Student).all()

    # 將鏈接交還給鏈接池
    session.close()


from threading import Thread

for i in range(20):
    t = Thread(target=task)
    t.start()

方式二：（推薦，基於Threading.local實現）
from sqlalchemy.orm import sessionmaker
from sqlalchemy import create_engine
from sqlalchemy.orm import scoped_session
from models import Student,Course,Student2Course

engine = create_engine(
        "mysql+pymysql://root:123456@127.0.0.1:3306/s9day120?charset=utf8",
        max_overflow=0,  # 超過鏈接池大小外最多建立的鏈接
        pool_size=5,  # 鏈接池大小
        pool_timeout=30,  # 池中沒有線程最多等待的時間，不然報錯
        pool_recycle=-1  # 多久以後對線程池中的線程進行一次鏈接的回收（重置）
    )
SessionFactory = sessionmaker(bind=engine)
session = scoped_session(SessionFactory)


def task():
    ret = session.query(Student).all()
    # 將鏈接交還給鏈接池
    session.remove()


from threading import Thread

for i in range(20):
    t = Thread(target=task)
    t.start()

鏈接的兩種方式

#!/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)

"""
# 線程安全，基於本地線程實現每一個線程用同一個session
# 特殊的：scoped_session中有原來方法的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)


# ############# 執行ORM操做 #############
obj1 = Users(name="alex1")
session.add(obj1)



# 提交事務
session.commit()
# 關閉session
session.close()

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 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()

多線程執行示例

#!/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語句

#!/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='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操做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: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操做m2m

#!/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()

# 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()

其餘