Flask的sqlalchemy SQL练习

Posted 2021-01-12 知我几分

models.py from sqlalchemy import create_engine, Column, Integer, String, ForeignKey, Enum, UniqueConstraint from sqlalchemy.ext.declarative import declarative_base from sqlalchemy.orm import sessionmaker, relationship # 数据库配置信息 HOST = "127.0.0.1" PORT = "3306" DATABASE = "yangyu" USERNAME = "root" PASSWORD = "yang123" # 数据库的固定格式 DB_URL = "mysql+pymysql://{username}:{password}@{host}:{port}/{db}?charset-utf8".format( username=USERNAME, password=PASSWORD, host=HOST, port=PORT, db=DATABASE ) # 创建一个引擎 engine = create_engine(DB_URL) # 用declarative_base根据engine创建一个ORM基类 Base = declarative_base(engine) # 创建一个ORM模型，这个模型继承sqlalchemy给我们提供基类，即上面的Base class Depart(Base): """部门表""" __tablename__ = "depart" id = Column(Integer, primary_key=True, autoincrement=True) caption = Column(String(64), nullable=False) def __str__(self): return self.caption def __repr__(self): return self.__str__() class Student(Base): """学生表""" __tablename__ = "student" id = Column(Integer, primary_key=True, autoincrement=True) name = Column(String(32), nullable=False) gender = Column(Enum("男", "女")) # 外键关联 depart_id = Column(Integer, ForeignKey("depart.id")) # 与生成表结构无关,仅用于查询方便, backref指定反向查询字段名(起一个关联当前表的名字) departs = relationship("Depart", backref="student_list") def __str__(self): return self.name def __repr__(self): return self.__str__() class Teacher2Student(Base): """老师学生多对多关联表""" __tablename__ = "teacher2student" id = Column(Integer, primary_key=True, autoincrement=True) teacher_id = Column(Integer, ForeignKey("teacher.id")) student_id = Column(Integer, ForeignKey("student.id")) class Teacher2Depart(Base): """老师班级多对多关联表""" __tablename__ = "teacher2depart" id = Column(Integer, primary_key=True, autoincrement=True) teacher_id = Column(Integer, ForeignKey("teacher.id")) depart_id = Column(Integer, ForeignKey("depart.id")) __table_args__ = ( # 联合唯一索引,加速查找、不重复 UniqueConstraint(‘teacher_id‘, ‘depart_id‘, name=‘teacher_depart_id‘), # Index(‘st_id_name‘, ‘name‘, ‘extra‘), # 联合索引,加速查找 ) class Teacher(Base): """老师表""" __tablename__ = "teacher" id = Column(Integer, primary_key=True, autoincrement=True) name = Column(String(64), nullable=False) # secondary指定多对多中记录的排序方式，前面的代表关联类名字，后面是反向查询本表的字段名 students = relationship("Student", secondary="teacher2student", backref="teacher_list") departs = relationship("Depart", secondary="teacher2depart", backref="teacher_list") def __str__(self): return self.name def __repr__(self): return self.__str__() class Course(Base): """课程表""" __tablename__ = "course" id = Column(Integer, primary_key=True, autoincrement=True) title = Column(String(64), nullable=False) teacher_id = Column(Integer, ForeignKey("teacher.id")) scores = relationship("Score", backref="course_list") teachers = relationship("Teacher", backref="course_list") def __str__(self): return self.title def __repr__(self): return self.__str__() class Score(Base): """成绩表""" __tablename__ = "score" id = Column(Integer, primary_key=True, autoincrement=True) number = Column(Integer, nullable=False) student_id = Column(Integer, ForeignKey("student.id")) course_id = Column(Integer, ForeignKey("course.id")) students = relationship("Student", backref="score_list") def __str__(self): return self.number def __repr__(self): return self.__str__() # 将创建好的ORM模型，映射到数据库中 Base.metadata.create_all() # ORM对数据库操作需要构建一个session对象 session = sessionmaker(engine)() sql练习.py from learn.models import * from learn.models import session # 增(需要什么字段添加什么字段) obj = Depart(caption="Go全栈") session.add(obj) session.commit() session.add_all([Course(title="Go基础"), Course(title="Java三大器")]) session.commit() session.add_all([ Student(name="小五"), Depart(caption="间谍"), Teacher(name="海哥"), Score(number=90), Course(title="翻盘一号"), ]) session.commit() # 创建一个新老师，并给他指定两个新学生 obj = Teacher(name="二筒") obj.students = [Student(name="小五", gender="男", class_id=2), Student(name="二胖", gender="男", class_id=3)] session.add(obj) session.commit() # 查询Python班级有多少学生 val = session.query(ClassTable.caption, Student.name).filter(ClassTable.id==1).all() 查询课程id大于2的所有课程 val = session.query(Course).filter(Course.id > 2).all() # 找到钢蛋的老师 val = session.query(Student).filter(Student.name=="钢蛋").first() for item in val.teacher_list: print(item) # 查看小王老师教的课程 val = session.query(Teacher).filter(Teacher.name=="小王").first() for item in val.courses: print(item) # 删 session.query(Teacher2Student).filter(Teacher2Student.id > 4).delete() session.commit() session.close() # 修改学生属性和关联课程 session.query(Student).filter(Student.id == 8).update({Student.gender: "女"}) session.query(Student).filter(Student.id == 9).update({Student.gender: "女"}) session.query(Student).filter(Student.id == 10).update({Student.class_id: 2}) session.query(Student).filter(Student.id == 11).update({Student.class_id: 3}) session.commit()