SQLAlchemy 创建 增 删 改 查

Posted wyf20190411-

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SQLAlchemy

  是python 编程语言下的一款ORM框架,该框架建立在数据库API之上,使用关系对象映射进行数据库操作,简而言之急就是:将对象转为sql,然后使用数据api执行sql并获取执行结果。

  注:ORM 是一种思想  ;

    SQLZlchemy本身无法操作数据库,他必须依赖pysmysql等第三插件,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

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:[email protected]:port/dbname[?key=value&key=value...]
   
更多详见:http://docs.sqlalchemy.org/en/latest/dialects/index.html

安装:

  pip3 install SQLAlchemy

功能:使用所有组件对数据库进行操作,根据类创建对象,对象转换成sql,执行sql

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
 
engine = create_engine("mysql+pymysql://root:[email protected]:3306/t1", max_overflow=5)
 
Base = declarative_base()
 
# 创建单表
class Users(Base):
    __tablename__ = users
    id = Column(Integer, primary_key=True)
    name = Column(VARCHAR(32))
    extra = Column(VARCHAR(16))
 
    __table_args__ = (
    UniqueConstraint(id, name, name=uix_id_name),
        Index(ix_id_name, name, extra),
    )
 
 
# 一对多
class Favor(Base):
    __tablename__ = favor
    nid = Column(Integer, primary_key=True)
    caption = Column(VARCHAR(50), default=red, unique=True)
 
 
class Person(Base):
    __tablename__ = person
    nid = Column(Integer, primary_key=True)
    name = Column(VARCHAR(32), index=True, nullable=True)
    favor_id = Column(Integer, ForeignKey("favor.nid"))
 
 
# 多对多
class Group(Base):
    __tablename__ = group
    id = Column(Integer, primary_key=True)
    name = Column(VARCHAR(64), unique=True, nullable=False)
    port = Column(Integer, default=22)
 
 
class Server(Base):
    __tablename__ = server
 
    id = Column(Integer, primary_key=True, autoincrement=True)
    hostname = Column(VARCHAR(64), unique=True, nullable=False)
 
 
class ServerToGroup(Base):
    __tablename__ = servertogroup
    nid = Column(Integer, primary_key=True, autoincrement=True)
    server_id = Column(Integer, ForeignKey(server.id))
    group_id = Column(Integer, ForeignKey(group.id))
  
def init_db():
    Base.metadata.create_all(engine)

def drop_db():
    Base.metadata.drop_all(engine)

操作表

# 创建单表
class Users(Base):
    __tablename__ = users
    id = Column(Integer, primary_key=True)
    name = Column(VARCHAR(32))
    extra = Column(VARCHAR(16))

    __table_args__ = (
    UniqueConstraint(id, name, name=uix_id_name),
        Index(ix_id_name, name, extra),
    )

    def __repr__(self):
        return "%s-%s" %(self.id, self.name)

# 一对多
class Favor(Base):
    __tablename__ = favor
    nid = Column(Integer, primary_key=True)
    caption = Column(VARCHAR(50), default=red, unique=True)

    def __repr__(self):
        return "%s-%s" %(self.nid, self.caption)

class Person(Base):
    __tablename__ = person
    nid = Column(Integer, primary_key=True)
    name = Column(String(32), index=True, nullable=True)
    favor_id = Column(Integer, ForeignKey("favor.nid"))
    # 与生成表结构无关,仅用于查询方便
    favor = relationship("Favor", backref=pers)

# 多对多
class ServerToGroup(Base):
    __tablename__ = servertogroup
    nid = Column(Integer, primary_key=True, autoincrement=True)
    server_id = Column(Integer, ForeignKey(server.id))
    group_id = Column(Integer, ForeignKey(group.id))
    group = relationship("Group", backref=s2g)
    server = relationship("Server", backref=s2g)

class Group(Base):
    __tablename__ = group
    id = Column(Integer, primary_key=True)
    name = Column(String(64), unique=True, nullable=False)
    port = Column(Integer, default=22)
    # group = relationship(Group,secondary=ServerToGroup,backref=host_list)


class Server(Base):
    __tablename__ = server

    id = Column(Integer, primary_key=True, autoincrement=True)
    hostname = Column(String(64), unique=True, nullable=False)


def init_db():
    Base.metadata.create_all(engine)

def drop_db():
    Base.metadata.drop_all(engine)

Session = sessionmaker(bind=engine)
session = Session()

增加

## 增加一条数据
obj = Users(name="alex0", extra=sb)
session.add(obj)

## 增加多条数据
session.add_all([
    Users(name="alex1", extra=sb),
    Users(name="alex2", extra=sb),
])
session.commit()
session.close()

查询

ret = session.query(Users).all()
ret = session.query(Users.name, Users.extra).all()
ret = session.query(Users).filter_by(name=alex).all()
ret = session.query(Users).filter_by(name=alex).first()

修改

session.query(Users).filter(Users.id > 2).update("name" : "099")
session.commit()

删除

session.query(Users).filter(Users.id > 2).delete()
session.commit()

高级操作    通配符     限制  limit       排序        分组         条件查询          链表

# 条件
ret = session.query(Users).filter_by(name=alex).all()
ret = session.query(Users).filter(Users.id > 1, Users.name == eric).all()
ret = session.query(Users).filter(Users.id.between(1, 3), Users.name == eric).all()
ret = session.query(Users).filter(Users.id.in_([1,3,4])).all()
ret = session.query(Users).filter(~Users.id.in_([1,3,4])).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 > 3, Users.name == eric)).all()
ret = session.query(Users).filter(or_(Users.id < 2, Users.name == eric)).all()
ret = session.query(Users).filter(
    or_(
        Users.id < 2,
        and_(Users.name == eric, Users.id > 3),
        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  limit 
ret = session.query(Users)[1:2]

# 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.min(Users.id)).group_by(Users.name).all()

ret = session.query(
    func.max(Users.id),
    func.min(Users.id)).group_by(Users.name).having(func.min(Users.id) >2).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()

 

 

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