SQLAlchemy（ORM框架）

2024-08-27 22:56:09

SQLAlchemy

SQLAlchemy概述

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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...]

更多详见：http://docs.sqlalchemy.org/en/latest/dialects/index.html

数据库操作的几种方式：

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from sqlalchemy import create_engine

engine = create_engine("mysql+mysqldb://root:123@127.0.0.1:3306/s11", max_overflow=5)

#max_overflow是在初始线程数量的基础上，还能最多建立几个进程

engine.execute(

"INSERT INTO ts_test (a, b) VALUES ('2', 'v1')"

)

engine.execute(

"INSERT INTO ts_test (a, b) VALUES (%s, %s)",

((555, "v1"),(666, "v1"),)

)

engine.execute(

"INSERT INTO ts_test (a, b) VALUES (%(id)s, %(name)s)",

id=999, name="v1"

)

result = engine.execute('select * from ts_test')

result.fetchall()

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from sqlalchemy import create_engine

engine = create_engine("mysql+mysqldb://root:123@127.0.0.1:3306/s11", max_overflow=5)

# 事务操作

with engine.begin() as conn:

conn.execute("insert into table (x, y, z) values (1, 2, 3)")

conn.execute("my_special_procedure(5)")

conn = engine.connect()

# 事务操作

with conn.begin():

conn.execute("some statement", {'x':5, 'y':10})

在mysql里用命令“show status like 'Threads%';”,能观察到连接线程数‘Threads_connected’的变化。

2、使用 Schema Type/SQL Expression Language/Engine/ConnectionPooling/Dialect 进行数据库操作

Engine使用Schema Type创建一个特定的结构对象，之后通过SQL Expression Language将该对象转换成SQL语句，然后通过 ConnectionPooling 连接数据库，再然后通过 Dialect 执行SQL，并获取结果。

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from sqlalchemy import create_engine, Table, Column, Integer, String, MetaData, ForeignKey

metadata = MetaData()

user = Table('user', metadata,

Column('id', Integer, primary_key=True),

Column('name', String(20)),

)

color = Table('color', metadata,

Column('id', Integer, primary_key=True),

Column('name', String(20)),

)

engine = create_engine("mysql+mysqldb://root:123@127.0.0.1:3306/s11", max_overflow=5)

metadata.create_all(engine)

# metadata.clear()

# metadata.remove()

增删改查：

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from sqlalchemy import create_engine, Table, Column, Integer, String, MetaData, ForeignKey

metadata = MetaData()

user = Table('user', metadata,

Column('id', Integer, primary_key=True),

Column('name', String(20)),

)

color = Table('color', metadata,

Column('id', Integer, primary_key=True),

Column('name', String(20)),

)

engine = create_engine("mysql+mysqldb://root:123@127.0.0.1:3306/s11", max_overflow=5)

conn = engine.connect()

# 创建SQL语句，INSERT INTO "user" (id, name) VALUES (:id, :name)

conn.execute(user.insert(),{'id':7,'name':'seven'})

conn.close()

# sql = user.insert().values(id=123, name='wu')

# conn.execute(sql)

# conn.close()

# sql = user.delete().where(user.c.id > 1)

# sql = user.update().values(fullname=user.c.name)

# sql = user.update().where(user.c.name == 'jack').values(name='ed')

# sql = select([user, ])

# sql = select([user.c.id, ])

# sql = select([user.c.name, color.c.name]).where(user.c.id==color.c.id)

# sql = select([user.c.name]).order_by(user.c.name)

# sql = select([user]).group_by(user.c.name)

# result = conn.execute(sql)

# print result.fetchall()

# conn.close()

更多内容详见：

中文：http://www.jianshu.com/p/e6bba189fcbd

英文：http://docs.sqlalchemy.org/en/latest/core/expression_api.html （比中文的全面）

注：SQLAlchemy无法修改表结构，如果需要可以使用SQLAlchemy开发者开源的另外一个软件Alembic来完成。

3、使用 ORM/Schema Type/SQL Expression Language/Engine/ConnectionPooling/Dialect 所有组件对数据进行操作

根据类创建对象，对象转换成SQL，执行SQL。

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from sqlalchemy.ext.declarative import declarative_base

from sqlalchemy import Column, Integer, String

from sqlalchemy.orm import sessionmaker

from sqlalchemy import create_engine

engine = create_engine("mysql+mysqldb://root:123@127.0.0.1:3306/s11", max_overflow=5)

Base = declarative_base()

class User(Base):

__tablename__ = 'users'

id = Column(Integer, primary_key=True)

name = Column(String(50))

# 寻找Base的所有子类，按照子类的结构在数据库中生成对应的数据表信息

# Base.metadata.create_all(engine)

Session = sessionmaker(bind=engine)

session = Session()

# ########## 增 ##########

# u = User(id=2, name='sb')

# session.add(u)

# session.add_all([

# User(id=3, name='sb'),

# User(id=4, name='sb')

# ])

# session.commit()

# ########## 删除 ##########

# session.query(User).filter(User.id > 2).delete()

# session.commit()

# ########## 修改 ##########

# session.query(User).filter(User.id > 2).update({'cluster_id' : 0})

# session.commit()

# ########## 查 ##########

# ret = session.query(User).filter_by(name='sb').first()

# ret = session.query(User).filter_by(name='sb').all()

# print ret

# ret = session.query(User).filter(User.name.in_(['sb','bb'])).all()

# print ret

# ret = session.query(User.name.label('name_label')).all()

# print ret,type(ret)

# ret = session.query(User).order_by(User.id).all()

# print ret

# ret = session.query(User).order_by(User.id)[1:3]

# print ret

# session.commit()

更多功能参见文档，猛击这里下载PDF

来源：武sir博客http://www.cnblogs.com/wupeiqi/

来自为知笔记(Wiz)

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