sqlalchemy-数据库操作

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 = 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"))

    # 与生成表结构无关，仅用于查询方便
    hobby = relationship("Hobby", backref='pers')


# ##################### 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(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')


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@xx.xx.xx.x: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)


def drop_db():
    """
    根据类删除数据库表
    :return: 
    """
    engine = create_engine(
        "mysql+pymysql://root:123@xx.xx.xx.x: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()

链接测试↓

import time
import threading
import sqlalchemy
from sqlalchemy import create_engine
from sqlalchemy.engine.base import Engine

engine = create_engine(
    "mysql+pymysql://root:123@47.93.4.198:3306/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）
)

from sqlalchemy.pool import _ConnectionFairy
def task(arg):
    conn = engine.raw_connection()
    print('你到了',conn.connection)
    cursor = conn.cursor()
    cursor.execute(
        "select * from users"
    )
    result = cursor.fetchall()
    import time
    time.sleep(5)
    cursor.close()
    conn.close()


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

表操作：↓

from sqlalchemy.orm import sessionmaker
from sqlalchemy import create_engine
from models import Users,Person,Hobby

engine = create_engine(
        "mysql+pymysql://root:123@47.93.4.198:3306/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）
)
Session = sessionmaker(bind=engine)

# 每次执行数据库操作时，都需要创建一个session，申请一个连接
session = Session()

# ############# 执行ORM操作 #############
# obj1 = Users(name="alex1")
# obj2 = Users(name="alex2")
# session.add(obj1)
# session.add(obj2)

# session.add_all([
#         Users(name="alex3"),
#         Users(name="alex4")
# ])

# 提交事务
# session.commit()

from sqlalchemy import and_, or_
ret = session.query(Person).join(Hobby,Person.hobby_id==Hobby.id,isouter=True)
# ret = session.query(Person).join(Hobby,and_(Person.hobby_id==Hobby.id,Person.id >2),isouter=True)
print(ret)


# 关闭session
session.close()