sqlalchemy 一对多的增删改查操作

一、创建表以及数据库的连接

# 一对多建表操作, 关系型表
from crud.create_table import engine
from sqlalchemy.ext.declarative import declarative_base

Base = declarative_base()
from sqlalchemy import String, Column, Integer, ForeignKey
from sqlalchemy.orm import relationship

"""
正向按字段，反向按backref
"""


class Student(Base):
    __tablename__ = "student"
    id = Column(Integer, primary_key=True, autoincrement=True)
    name = Column(String(32),)
    school_id = Column(Integer, ForeignKey("school.id"))

    stu2sch = relationship("School", backref="sch2stu")


class School(Base):
    __tablename__ = "school"
    id = Column(Integer, primary_key=True)
    name = Column(String(32))


Base.metadata.create_all(engine)

二、数据的增删改查

1、数据的添加

from crud.create_table import engine
from sqlalchemy.orm import sessionmaker
from crud_foreignkey.create_table_foreignkey import Student, School

Session = sessionmaker(engine)
db_session = Session()

# 添加数据1
# 创建学校
# sch_obj = School(name="北京校区")
# db_session.add(sch_obj)
"""
查询出学校的id,将学校的id赋给学生对象
"""
sch = db_session.query(School).filter(School.name == '北京校区').first()
stu_obj = Student(name='张三', school_id=sch.id)
db_session.add(stu_obj)

# 添加数据2 正向relationship
"""
1、创建学生对象,
2、在学生对象里添加学校对象:stu2sch=School(name="上海校区")
"""
# stu_obj = Student(name="李四", stu2sch=School(name="上海校区"))
# db_session.add(stu_obj)

# 添加数据3 反向relationship
"""
1、反向创建学校对象
2、学校对象.sch2stu = [多个学生对象]
"""
sch_obj = School(name="深圳校区")
# 添加多个对象
sch_obj.sch2stu = [Student(name="赵六"), Student(name='陈琦')]
db_session.add(sch_obj)


db_session.commit()
db_session.close()

2、数据的查询

from crud_foreignkey.create_table_foreignkey import School, Student
from crud.create_table import engine
from sqlalchemy.orm import sessionmaker

Session = sessionmaker(engine)
db_session = Session()

# 正向查询
stu = db_session.query(Student).all()
for row in stu:
    print(row.id, row.name, row.school_id, row.stu2sch.name)
"""
通过学生表去查询校区表，根据stu2sch.去查询
"""
# 反向查询
sch = db_session.query(School).all()
for school in sch:
    for student in school.sch2stu:
        print(student.name, student.id, student.stu2sch.name)
# print(school.sch2stu) 打印出每个校区的所有学生 如下:
"""
[<crud_foreignkey.create_table_foreignkey.Student object at 0x0000028105137898>]
[<crud_foreignkey.create_table_foreignkey.Student object at 0x0000028105137668>]
[<crud_foreignkey.create_table_foreignkey.Student object at 0x0000028105137908>, 
<crud_foreignkey.create_table_foreignkey.Student object at 0x0000028105137978>]

"""
db_session.commit()
db_session.close()

3、数据的修改

from crud.create_table import engine
from crud_foreignkey.create_table_foreignkey import School, Student
from sqlalchemy.orm import sessionmaker
Session = sessionmaker(engine)
db_session = Session()

# 修改数据，修改学生的school_id
sch = db_session.query(School).filter(School.name == "上海校区").first()
db_session.query(Student).filter(Student.name == "陈琦").update({"school_id": sch.id})

db_session.commit()
db_session.close()

4、数据的删除

from crud.create_table import engine
from crud_foreignkey.create_table_foreignkey import School, Student
from sqlalchemy.orm import sessionmaker
Session = sessionmaker(engine)
db_session = Session()

# 删除所有上海校区的学生
sch_obj = db_session.query(School).filter(School.name == '上海校区').first()
db_session.query(Student).filter(Student.id == sch_obj.id).delete()

db_session.commit()
db_session.close()

三、其他的查询方式

ret = session.query(User).filter_by(name='DragonFire').all()
ret = session.query(User).filter(User.id > 1, User.name == 'DragonFire').all()
ret = session.query(User).filter(User.id.between(1, 3), User.name == 'DragonFire').all() # between 大于1小于3的
ret = session.query(User).filter(User.id.in_([1,3,4])).all() # in_([1,3,4]) 只查询id等于1,3,4的
ret = session.query(User).filter(~User.id.in_([1,3,4])).all() # ~xxxx.in_([1,3,4]) 查询不等于1,3,4的
ret = session.query(User).filter(User.id.in_(session.query(User.id).filter_by(name='DragonFire'))).all() 子查询
from sqlalchemy import and_, or_
ret = session.query(User).filter(and_(User.id > 3, User.name == 'DragonFire')).all()
ret = session.query(User).filter(or_(User.id < 2, User.name == 'DragonFire')).all()
ret = session.query(User).filter(
    or_(
        User.id < 2,
        and_(User.name == 'eric', User.id > 3),
        User.extra != ""
    )).all()
# select * from User where id<2 or (name="eric" and id>3) or extra != "" 

# 通配符
ret = db_session.query(User).filter(User.name.like('e%')).all()
ret = db_session.query(User).filter(~User.name.like('e%')).all()

# 限制
ret = db_session.query(User)[1:2]

# 排序
ret = db_session.query(User).order_by(User.name.desc()).all()
ret = db_session.query(User).order_by(User.name.desc(), User.id.asc()).all()

# 分组
from sqlalchemy.sql import func

ret = db_session.query(User).group_by(User.extra).all()
ret = db_session.query(
    func.max(User.id),
    func.sum(User.id),
    func.min(User.id)).group_by(User.name).all()

ret = db_session.query(
    func.max(User.id),
    func.sum(User.id),
    func.min(User.id)).group_by(User.name).having(func.min(User.id) >2).all()

四、修改操作的其他方式

#高级版更新操作
from create_table import User,engine
from sqlalchemy.orm import sessionmaker

Session = sessionmaker(engine)
db_session = Session()

#直接修改
# db_session.query(User).filter(User.id > 0).update({"name" : "099"})

#在原有值基础上添加 
db_session.query(User).filter(User.id > 0).update({User.name: User.name + "099"}, synchronize_session=False)
db_session.commit()

#在原有值基础上添加 
# db_session.query(User).filter(User.id > 0).update({"age": User.age + 1}, synchronize_session="evaluate")
# db_session.commit()