SQLAlchemyの增删改查

Posted 2020-11-02 拜悦神教

用a*my写原味sql 

from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import Column, Integer, String
from sqlalchemy import create_engine

Base = declarative_base()


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


# 数据库连接相关
engine = create_engine("mysql+pymysql://root:[email protected]:3306/day128?charset=utf8")


def init_db():
    # 创建表
    Base.metadata.create_all(engine)


def drop_db():
    # 删除表
    # Base.metadata.drop_all(engine)
    pass


if __name__ == ‘__main__‘:
    # drop_db()
    init_db()

models

from sqlalchemy import create_engine

engine = create_engine("mysql+pymysql://root:[email protected]:3306/day128?charset=utf8")
cur = engine.execute(‘SELECT * FROM users‘)
result = cur.fetchall()
print(result)

原味sql

用a*my写ORM增删改查 

from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import Column, Integer, String, UniqueConstraint, Index, DateTime, ForeignKey
from sqlalchemy import create_engine
from sqlalchemy.orm import relationship
import datetime

Base = declarative_base()


class Classes(Base):
    __tablename__ = ‘classes‘
    id = Column(Integer, primary_key=True, autoincrement=True)
    name = Column(String(32), nullable=False, unique=True)


class Student(Base):
    __tablename__ = ‘student‘
    id = Column(Integer, primary_key=True, autoincrement=True)
    username = Column(String(32), nullable=False, index=True)
    password = Column(String(64), nullable=False)
    ctime = Column(DateTime, default=datetime.datetime.now)
    class_id = Column(Integer, ForeignKey("classes.id"))
    # 关联字段     backref = 反向字段
    cls = relationship("Classes", backref=‘stus‘)


class Hobby(Base):
    __tablename__ = ‘hobby‘
    id = Column(Integer, primary_key=True)
    caption = Column(String(50), default=‘篮球‘)


class Student2Hobby(Base):
    __tablename__ = ‘student2hobby‘
    id = Column(Integer, primary_key=True, autoincrement=True)
    student_id = Column(Integer, ForeignKey(‘student.id‘))
    hobby_id = Column(Integer, ForeignKey(‘hobby.id‘))

    __table_args__ = (
        UniqueConstraint(‘student_id‘, ‘hobby_id‘, name=‘uix_student_id_hobby_id‘),
        # Index(‘ix_id_name‘, ‘name‘, ‘extra‘),
    )


def init_db():
    # 数据库连接相关
    engine = create_engine("mysql+pymysql://root:[email protected]:3306/day128?charset=utf8")
    # 创建表
    Base.metadata.create_all(engine)


def drop_db():
    engine = create_engine("mysql+pymysql://root:[email protected]:3306/day128?charset=utf8")
    # 删除表
    Base.metadata.drop_all(engine)


if __name__ == ‘__main__‘:
    # drop_db()
    init_db()

0.models

import models
from sqlalchemy.orm import sessionmaker
from sqlalchemy import create_engine

engine = create_engine("mysql+pymysql://root:[email protected]:3306/day128?charset=utf8")
XXXXXX = sessionmaker(bind=engine)
session = XXXXXX()

# 单条插入
# obj = models.Classes(name=‘第一期‘)
# session.add(obj)
# session.commit()

# 多条插入
# objs = [
#     models.Classes(name=‘第二期‘),
#     models.Classes(name=‘第三期‘),
#     models.Classes(name=‘第四期‘),
#     models.Classes(name=‘第五期‘),
# ]
#
# session.add_all(objs)
# session.commit()

session.close()

1.增

import models
from sqlalchemy.orm import sessionmaker
from sqlalchemy import create_engine

engine = create_engine("mysql+pymysql://root:[email protected]:3306/day128?charset=utf8")
session = sessionmaker(bind=engine)()

result = session.query(models.Classes).all()
for item in result:
    print(item.id,
          item.name)

session.close()

2.查

import models
from sqlalchemy.orm import sessionmaker
from sqlalchemy import create_engine

engine = create_engine("mysql+pymysql://root:[email protected]:3306/day128?charset=utf8")
session = sessionmaker(bind=engine)()

session.query(models.Classes).filter(models.Classes.id>4).delete()


session.commit()
session.close()

3.删

import models
from sqlalchemy.orm import sessionmaker
from sqlalchemy import create_engine

engine = create_engine("mysql+pymysql://root:[email protected]:3306/day128?charset=utf8")
session = sessionmaker(bind=engine)()

session.query(models.Classes).filter(models.Classes.id > 0).update({models.Classes.name: models.Classes.name + ‘666‘},
                                                                   synchronize_session=False)

session.commit()
session.close()

4.改

import models
from sqlalchemy.orm import sessionmaker
from sqlalchemy import create_engine,text

engine = create_engine("mysql+pymysql://root:[email protected]:3306/day128?charset=utf8")
session = sessionmaker(bind=engine)()

# 1 别名查询
result = session.query(models.Classes.id, models.Classes.name.label(‘xx‘)).all()    # label 起别名
for item in result:
    print(item.id, item.xx)

# 2. filter接表达式/filter_by接参数
r3 = session.query(models.Classes).filter(models.Classes.name == "anne").all()
r4 = session.query(models.Classes).filter_by(name=‘anne‘).all()

# 3. 子查询
result = session.query(models.Classes).from_statement(text("SELECT * FROM classes where name=:name")).params(name=‘ed‘).all()
result = session.query(models.Classes).from_statement(text("SELECT * FROM classes where name=:name")).params(name=‘ed‘)
# 子查询
ret = session.query(models.Classes).filter(models.Classes.id.in_(session.query(models.Classes.id).filter_by(name=‘eric‘))).all()
# 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)

session.close()

5.子查询

import models
from sqlalchemy.orm import sessionmaker
from sqlalchemy import create_engine

engine = create_engine("mysql+pymysql://root:[email protected]:3306/day128?charset=utf8")
session = sessionmaker(bind=engine)()

1.在学生表中插入数据
obj = models.Student(username=‘anne‘, password=123, class_id=3)
obj = models.Student(username=‘bob‘, password=123, class_id=3)
obj = models.Student(username=‘fry‘, password=123, class_id=3)
session.add(obj)
session.commit()

2. 在学生表中找到anne
obj = session.query(models.Student).filter(models.Student.username==‘anne‘).first()
print(obj.id)

3. 找到所有学生,并打印信息
方法1
objs =session.query(models.Student).all()
for obj in objs:
    cls_obj = session.query(models.Classes).filter(models.Classes.id ==obj.class_id).first()
    print(obj.id,obj.username,obj.class_id,cls_obj.name)
方法2
objs = session.query(models.Student.id,
                     models.Student.username,
                     models.Classes.name).join(models.Classes,isouter=True).all()
print(objs)
方法3
objs = session.query(models.Student).all()
for item in objs:
    print(item.id, item.username, item.class_id, item.cls.name)

# 4. 第三期所有的学生
obj = session.query(models.Classes).filter(models.Classes.id == 3).first()
student_list = obj.stus  # 反向查询
for item in student_list:
    print(item.id, item.username)

session.close()

6.跨表

.