v0.1 fastapi: route + model + orm
This commit is contained in:
geeker
@@ -0,0 +1,27 @@
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import pymysql.cursors
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# Connect to the database
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connection = pymysql.connect(
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host="localhost",
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user="geeker",
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password="geeker",
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database="fastapi_tutor",
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cursorclass=pymysql.cursors.DictCursor,
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)
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with connection:
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with connection.cursor() as cursor:
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# Create a new record
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sql = "INSERT INTO `users` (`email`, `password`) VALUES (%s, %s)"
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cursor.execute(sql, ("webmaster@python.org", "very-secret"))
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# connection is not autocommit by default. So you must commit to save
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# your changes.
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connection.commit()
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with connection.cursor() as cursor:
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# Read a single record
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sql = "SELECT `id`, `password` FROM `users` WHERE `email`=%s"
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cursor.execute(sql, ("webmaster@python.org",))
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result = cursor.fetchone()
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print(result)
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@@ -0,0 +1,4 @@
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id title content user_id created_at
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-- ---------- ------------- ------- --------------------------
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1 Alice 的第一篇 Hello world 1 2026-09-18 22:42:47.786259
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2 Alice 的第二篇 SQLAlchemy 真香 1 2026-09-18 22:42:48.010497
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@@ -0,0 +1,234 @@
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from sqlalchemy import create_engine, Column, Integer,String,DATETIME,DECIMAL, or_, and_,not_,func
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from sqlalchemy.orm import declarative_base, sessionmaker
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from datetime import datetime
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db_url = "mysql+pymysql://geeker:geeker@localhost:3306/fastapi_tutor?charset=utf8mb4"
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engine = create_engine(db_url, pool_size= 50, echo=True)
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Base = declarative_base() # 获取基类！
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class Order(Base): # python里的表名字
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__tablename__ = 'order_info_detail' # 实际数据库的表名字
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id = Column( Integer # 声明字段的数据类型
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, primary_key=True # 声明是主键
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, autoincrement=True # 声明是自增主键
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, comment='订单编号，自增主键' # 注释
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)
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title = Column( String(50) # 对应数据库的varchar类型
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,nullable=False # 不允许为null
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)
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price = Column(DECIMAL)
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userid = Column( Integer
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# ,ForeignKey('user_info_detail.id')
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,nullable=False ) # 外键约束
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create_date = Column(DATETIME
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, default=datetime.now # 默认值是当前时间
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)
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update_date = Column(DATETIME
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, default=datetime.now # 首次创建的时间跟更新时间一致
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, onupdate=datetime.now
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)
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class User(Base): # python里的表名字
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__tablename__ = 'user_info_detail' # 实际数据库的表名字
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id = Column( Integer # 声明字段的数据类型
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, primary_key=True # 声明是主键
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, autoincrement=True # 声明是自增主键
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, comment='用户编号，自增主键' # 注释
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)
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username = Column( String(50) # 对应数据库的varchar类型
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,nullable=False # 不允许为null
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,comment='用户名'
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)
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create_date = Column(DATETIME
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, default=datetime.now # 默认值是当前时间
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)
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update_date = Column(DATETIME
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, default=datetime.now # 首次创建的时间跟更新时间一致
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, onupdate=datetime.now
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)
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Base.metadata.create_all(engine) # 所有表创建 <- 只要数据库存在这个表了，就不会触发，也不会更新表结构
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# Order.__table__.create(engine,checkfirst = True) # 单张表的创建
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# 三、【表数据的新增】
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'''1.实例化数据库表模型类，得到具体的数据'''
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u1 = User( username='清风飞扬' )
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print( 'User1的属性：',u1.id,u1.username,u1.create_date,u1.update_date )
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u2 = User( username='北大青鸟' )
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print( 'User2的属性：',u2.username)
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'''2.将实例化好的数据，添加到数据库里'''
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# 拿到数据库会话管理工具
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Session = sessionmaker( bind=engine
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,autoflush=False # 是否开启自动刷新python新增的数据到实际的数据库内存缓存中
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,autocommit = False # 不自动提交数据，这个是真正提交到数据库磁盘永久生效的
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)
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session = Session() # 实例化一个数据库操作会话
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# session.add( u1 ) # 新增数据到数据库里
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# session.add( u2 )
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session.commit() # 提交，永久生效，注意提交后不能回滚
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print(session.query(User).all())
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#
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# # session.rollback() # 回滚，事务没有提交前，dml操作可以回滚
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# session.close() # 关闭数据操作会话
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#
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#
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# '''
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# 等价于sql语句：
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# insert into user_info_detail(username) values('清风飞扬');
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# insert into user_info_detail(username) values('北大青鸟');
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# '''
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#
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# # 四、【表数据的更改】
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# session = Session() # 实例化一个数据库操作会话
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# print(f'{session.query(User)=}, {session.query(User).all()=}')
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# session.query(User)\
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# .filter( User.username == '北大青鸟' )\
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# .update( {"username":'沃林数智'
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# , "create_date":"2000-10-10"
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# } # 同时更新多个字段
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# )
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# session.commit()
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# '''
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# 多个复合条件：
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# filter( 条件1,条件2，条件3.. ) # and的关系
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#
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# filter( or_( 条件1,条件2), not_(条件2),and_(条件1,条件2) )
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#
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# session.query(表模型).filter(条件1).filter(条件2).filter(条件3) 条件可以拼接成and的关系
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#
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# or_: 函数里的条件都是 or 的关系
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# and_: 函数里的条件是 and 的关系
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# not_ : 将条件的结果进行取反
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# '''
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#
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# # 五、【表数据的删除】
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# try:
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# session.query( User ).filter( User.username == '清风飞扬' ).delete() # 只要命中就删除
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# session.commit()
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# except:
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# session.rollback() # 如果报错，就回滚
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#
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# # 清空数据，并且重置自增主键 truncate table 表名; 无法回滚
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# # session.execute( text( "truncate table user_info_detail" ) ) # 直接书写原生的sql语句
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# # 可以select、update、delete全部支持
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'''1.单表基础查询'''
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# ① 单条数据查询 first(),返回的是一个查询结果对象
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r1 = session.query(User).first()
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print('获取单个查询结果对象：',r1)
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print(r1.id,r1.usernmae,r1.create_date,r1.update_date)
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# ② 全量查询 all() , 返回的是一个列表list
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r2 = session.query(User).all()
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print('获取多个查询结果对象：',r2)
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for i in range( len(r2) ):
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print(f'第{i+1}行数据：',r2[i].id,r2[i].usernmae,r2[i].create_date,r2[i].update_date)
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q = session.query(User) # 得到一个查询语句对象
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r3 = q.all() # 获取查询语句对象的所有内容
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print(q)
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print(r3)
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# ③ where 条件查询
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r4 = session.query(User).filter( or_(User.id == 1, User.usernmae == '李四') ).all()
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for i in r4:
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print(i.id,i.usernmae)
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# ④ like模糊匹配查询
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r5 = session.query(User).where( User.usernmae.like('%三%') ).all()
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for i in r5:
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print('like模糊匹配：',i.id, i.usernmae)
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# ⑤ order by排序
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r5 = session.query(User).order_by(User.id.desc(), User.usernmae).all()
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for i in r5:
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print('排序：', i.id, i.usernmae)
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# ⑥ limit 分页
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'''
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分页公式：
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原生sql：limit( (页数-1)*每页数据量, 每页数据量 )
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orm里： offset( (页数-1)*每页数据量 ).limit(每页数据量)
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'''
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n = 1 # 页数
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m = 2 # 每页数据量
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r6 = session.query(User).offset((n-1)*m).limit(m).all()
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for i in r6:
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print('分页：', i.id, i.usernmae)
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'''2.分组聚合group by'''
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'''
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select usernmae,count(1)
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from user_info_detail
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group by usernmae
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having count(1) >= 2
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'''
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r7 = session.query(User.usernmae,func.count(User.id).label('num')).\
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group_by( User.usernmae ).\
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having( func.count(User.id) >= 2 ).\
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all()
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for i in r7:
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print('分组聚合：',i.usernmae,i.num)
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'''
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func函数支持：max、min、sum、count、avg常用的聚合函数
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用法： func.count(聚合的字段)
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'''
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'''3.多表关联查询join内连接/outerjoin左连接'''
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r8 = session.query(User.id.label('user_id') , User.usernmae, Order.id.label('order_id'), Order.title ).\
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join( Order, User.id == Order.userid ).\
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order_by(User.id).\
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all()
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for i in r8:
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print('多表关联内连接：',i.user_id,i.usernmae,i.order_id,i.title)
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# outerjoin(谁放在里面，谁就是从表)
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r8 = session.query(User.id.label('user_id') , User.usernmae, Order.id.label('order_id'), Order.title ).\
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outerjoin( Order, User.id == Order.userid ).\
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order_by(User.id).\
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all()
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for i in r8:
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print('多表关联左连接：',i.user_id,i.usernmae,i.order_id,i.title)
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'''
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select ——> session.query( 表模型名 )
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from 表1
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join 表2 on 条件 ——> join(连接的表，条件) / outerjoin(连接的表，条件)
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where 筛选条件 ——> filter(条件)
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group by 分组字段 ——> group_by(分组的字段)
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having 分组后过滤 ——> having(过滤的条件)
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order by 排序 ——> order_by( 排序的字段.desc() )
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limit 分页 ——> offset(偏移量).limit(数据量)
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'''
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n = 1 # 页数
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m = 2 # 每页数据量
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r9 = session.query(User.usernmae,Order.title,func.count(1).label('ordernum')).\
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join(Order,User.id == Order.userid).\
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filter(Order.title == '苹果').\
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group_by(User.usernmae,Order.title).\
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having(func.count(1) >= 1).\
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order_by(func.count(1).desc()).\
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offset((n-1)*m).limit(m).\
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all()
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for i in r9:
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print('完整的查询：',i.usernmae,i.title,i.ordernum)
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@@ -0,0 +1,180 @@
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from datetime import datetime
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from typing import List, Optional
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from sqlalchemy import (
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create_engine, String, Integer, ForeignKey, DateTime, select, func
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)
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from sqlalchemy.orm import (
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DeclarativeBase, Mapped, mapped_column, relationship,
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Session, selectinload
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)
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# ============================================================
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# 1. 定义 Base 和模型
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# ============================================================
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class Base(DeclarativeBase):
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"""所有模型的基类，SQLAlchemy 2.0 推荐写法"""
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pass
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class User(Base):
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__tablename__ = "users"
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id: Mapped[int] = mapped_column(primary_key=True, autoincrement=True)
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name: Mapped[str] = mapped_column(String(50), nullable=False)
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email: Mapped[str] = mapped_column(String(100), unique=True, nullable=False)
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created_at: Mapped[datetime] = mapped_column(DateTime, default=datetime.now)
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# 一对多：一个用户有多个文章
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posts: Mapped[List["Post"]] = relationship(
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back_populates="author",
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cascade="all, delete-orphan", # 删除用户时级联删除文章
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lazy="selectin" # 查询用户时自动预加载文章
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)
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def __repr__(self):
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return f"<User(id={self.id}, name='{self.name}', email='{self.email}')>"
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class Post(Base):
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__tablename__ = "posts"
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id: Mapped[int] = mapped_column(primary_key=True, autoincrement=True)
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title: Mapped[str] = mapped_column(String(200), nullable=False)
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content: Mapped[Optional[str]] = mapped_column(String(1000))
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user_id: Mapped[int] = mapped_column(ForeignKey("users.id"), nullable=False)
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created_at: Mapped[datetime] = mapped_column(DateTime, default=datetime.now)
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# 多对一：多篇文章属于一个用户
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author: Mapped["User"] = relationship(back_populates="posts")
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def __repr__(self):
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return f"<Post(id={self.id}, title='{self.title}', user_id={self.user_id})>"
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# ============================================================
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# 2. 创建引擎和表
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# ============================================================
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engine = create_engine("sqlite:///users_posts.db", echo=False)
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Base.metadata.create_all(engine)
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# ============================================================
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# 3. CRUD 操作
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# ============================================================
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def create_user(session: Session, name: str, email: str) -> User:
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user = User(name=name, email=email)
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session.add(user)
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session.commit()
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session.refresh(user) # 刷新以获取数据库生成的 id
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return user
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def create_post(session: Session, title: str, content: str, user_id: int) -> Post:
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post = Post(title=title, content=content, user_id=user_id)
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session.add(post)
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session.commit()
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session.refresh(post)
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return post
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def get_user_by_id(session: Session, user_id: int) -> Optional[User]:
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return session.get(User, user_id)
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def get_user_by_email(session: Session, email: str) -> Optional[User]:
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stmt = select(User).where(User.email == email)
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return session.execute(stmt).scalar_one_or_none()
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def get_all_users(session: Session) -> List[User]:
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stmt = select(User).order_by(User.id)
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return list(session.execute(stmt).scalars().all())
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def update_user_email(session: Session, user_id: int, new_email: str) -> bool:
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user = session.get(User, user_id)
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if not user:
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return False
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user.email = new_email
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session.commit()
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return True
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def delete_user(session: Session, user_id: int) -> bool:
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user = session.get(User, user_id)
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if not user:
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return False
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session.delete(user) # cascade 会自动删除关联的 posts
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session.commit()
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return True
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# ============================================================
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# 4. 复杂查询
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# ============================================================
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def get_users_with_post_count(session: Session):
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"""统计每个用户的文章数"""
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stmt = (
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select(User.name, func.count(Post.id).label("post_count"))
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.outerjoin(Post, User.id == Post.user_id)
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.group_by(User.id)
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.order_by(func.count(Post.id).desc())
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)
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return session.execute(stmt).all()
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def get_posts_by_user(session: Session, user_id: int) -> List[Post]:
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"""查询某个用户的所有文章"""
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stmt = select(Post).where(Post.user_id == user_id).order_by(Post.created_at.desc())
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return list(session.execute(stmt).scalars().all())
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# ============================================================
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# 5. 演示
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# ============================================================
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def main():
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with Session(engine) as session:
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# 清理旧数据（演示用）
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session.query(Post).delete()
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session.query(User).delete()
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session.commit()
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# 创建用户
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alice = create_user(session, "Alice", "alice@example.com")
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bob = create_user(session, "Bob", "bob@example.com")
|
||||
print("创建用户:", alice, bob)
|
||||
|
||||
# 创建文章
|
||||
create_post(session, "Alice 的第一篇", "Hello world", alice.id)
|
||||
create_post(session, "Alice 的第二篇", "SQLAlchemy 真香", alice.id)
|
||||
create_post(session, "Bob 的独苗", "Python ORM", bob.id)
|
||||
|
||||
# 查询
|
||||
print("\n所有用户:")
|
||||
for u in get_all_users(session):
|
||||
print(f" {u} -> 文章: {[p.title for p in u.posts]}")
|
||||
|
||||
print("\n用户文章数统计:")
|
||||
for name, count in get_users_with_post_count(session):
|
||||
print(f" {name}: {count} 篇")
|
||||
|
||||
# 更新
|
||||
update_user_email(session, alice.id, "alice_new@example.com")
|
||||
print("\n更新后:", get_user_by_id(session, alice.id))
|
||||
|
||||
# 删除（级联删除文章）
|
||||
delete_user(session, bob.id)
|
||||
print("\n删除 Bob 后，所有用户:")
|
||||
for u in get_all_users(session):
|
||||
print(f" {u}")
|
||||
|
||||
|
||||
if __name__ == "__main__":
|
||||
main()
|
||||
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Reference in New Issue
Block a user