pip3 install sqlalchemy
SQLAlchemy 与 Django 的 Models 区别：
Models 只是配置和使用比较简单,因为他是Django自带的ORM框架,也正是因为是Django原生的,所以兼容性远远不如SQLAlchemy
真正算得上全面的ORM框架必然是我们的SQLAlchemy ORM框架,它可以在任何使用SQL查询时使用
SQLAlchemy 如何使用:
使用概述：
单表增删改查：
# 通过SQLAlchemy创建数据表 # 1.导入SQLAlchemy from sqlalchemy.ext.declarative import declarative_base # 2.创建ORM模型基类 Base = declarative_base() # Django Model # 3.导入ORM对应数据库数据类型的字段 from sqlalchemy import Column, Integer, String # 4.创建ORM对象 class User(Base): __tablename__ = "user" id = Column(Integer, primary_key=True, autoincrement=True) name = Column(String(32), index=True) # 5.创建数据库连接 from sqlalchemy import create_engine engine = create_engine("mysql+pymysql://root:@127.0.0.1:3306/day127?charset=utf8") # 数据库连接创建完成 # 6.去数据库中创建与User所对应的数据表 # 去engine数据库中创建所有继承Base类的 ORM对象 Base.metadata.create_all(engine)
# 通过SQLAlchemy对数据表进行增删改查 # crud == 增删改查 # 想要操纵数据库 打开数据库连接 # from sqlalchemy import create_engine # engine = create_engine("mysql+pymysql://root:@127.0.0.1:3306/day127?charset=utf8") from create_table import engine # 创建会话 - 打开数据库连接 from sqlalchemy.orm import sessionmaker # 创建会话窗口 Session = sessionmaker(engine) # 打开会话窗口 db_session = Session() # 1.增加数据 == insert # # insert into user(name) values("DragonFire") # from create_table import User # user_obj = User(name="Ywb") # # 通过db_session已经打开会话窗口 提交数据 # db_session.add(user_obj) # insert into # # 执行会话窗口中的所有操作 # db_session.commit() #rud # db_session.close() # 2.增加批量数据 # from create_table import User # db_session.add_all([ # User(name="AlexDSB"), # User(name="DragonFire"), # User(name="赵丽颖") # ]) # # db_session.commit() # db_session.close() #扩展： # from create_table import User # user1 = User(name="666") # user2 = User(name="777") # user3 = User(name="888") # # db_session.add(user1) # db_session.add(user2) # db_session.add(user3) # # db_session.commit() # db_session.close()
# 查询 # 会话窗口 from sqlalchemy.orm import sessionmaker from create_table import engine Session = sessionmaker(engine) db_session = Session() from create_table import User # 1.简单查询 # select * from table # user_list = db_session.query(User).all() # for row in user_list: # print(row.id,row.name) # user = db_session.query(User).first() # print(user.id,user.name) # 2.带条件的查询 # user_list = db_session.query(User).filter(User.id == 4).all() # print(user_list[0].id,user_list[0].name) # user = db_session.query(User).filter_by(id=4).first() # print(user.id,user.name) # user_list = db_session.query(User).filter(User.id >= 4).all() # for row in user_list: # print(row.name,row.id) # 扩展 查看sql语句 # sql = db_session.query(User).filter(User.id >= 4) # print(sql)
# 更新修改数据 from sqlalchemy.orm import sessionmaker from create_table import engine, User Session = sessionmaker(engine) db_session = Session() # 1.修改数据 - 先查询预修改的数据 # update `user` set `name` = "666" where id = 1 # res = db_session.query(User).filter(User.name=="Ywb").update({"name":"武配齐"}) # print(res) # db_session.commit() # db_session.close() # res = db_session.query(User).filter(User.id >= 5).update({"name":123456}) # print(res) # db_session.commit() # db_session.close()
# 删除数据 from sqlalchemy.orm import sessionmaker from create_table import engine,User Session = sessionmaker(engine) db_session = Session() # 1.删除 - 先查询预删除的数据 # delete from user where id=5 # res = db_session.query(User).filter(User.id==5).delete() # print(res) # db_session.commit() # db_session.close() # 2.删除多条数据 # res = db_session.query(User).filter(User.name=="123456").delete() # print(res) # db_session.commit() # db_session.close()
一对多的增删改查：
# 一对多建表操作 from sqlalchemy.ext.declarative import declarative_base Base = declarative_base() from sqlalchemy import Column, Integer, String, ForeignKey from sqlalchemy.orm import relationship class Student(Base): __tablename__ = "student" id = Column(Integer, primary_key=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)) from sqlalchemy import create_engine engine = create_engine("mysql+pymysql://root:@127.0.0.1:3306/day127?charset=utf8") Base.metadata.create_all(engine)
# 添加数据 from sqlalchemy.orm import sessionmaker from create_table_ForeignKey import engine,Student,School Session = sessionmaker(engine) db_session = Session() # 1.添加数据 - 笨 # sch_obj = School(name="BD") # db_session.add(sch_obj) # db_session.commit() # # sch = db_session.query(School).filter(School.name == "BD").first() # stu_obj = Student(name="lbz",school_id=sch.id) # db_session.add(stu_obj) # db_session.commit() # db_session.close() # 2.添加数据 - 正向 relationship 版 # stu_obj = Student(name="lbz",stu2sch=School(name="BD")) # db_session.add(stu_obj) # db_session.commit() # db_session.close() # 3.添加数据 - 反向 relationship 版 # sch_obj = School(name="BD") # sch_obj.sch2stu = [Student(name="赵丽颖"),Student(name="柳岩")] # db_session.add(sch_obj) # db_session.commit() # db_session.close()
# 查询数据 from sqlalchemy.orm import sessionmaker from create_table_ForeignKey import engine,Student,School Session = sessionmaker(engine) db_session = Session() # 1.查询数据 - relationship 版 正向 # stu = db_session.query(Student).all() # for row in stu: # print(row.id,row.name,row.school_id,row.stu2sch.name) # 2.查询数据 - relationship 版 反向 # sch = db_session.query(School).all() # for school in sch: # for student in school.sch2stu: # print(school.id,school.name,student.name)
# 修改数据 from sqlalchemy.orm import sessionmaker from create_table_ForeignKey import engine,Student,School Session = sessionmaker(engine) db_session = Session() # 修改数据 sch = db_session.query(School).filter(School.name=="BD").first() db_session.query(Student).filter(Student.name == "赵丽颖").update({"school_id":sch.id}) db_session.commit() db_session.close()
from sqlalchemy.orm import sessionmaker from create_table_ForeignKey import engine,Student,School Session = sessionmaker(engine) db_session = Session() # 删除数据 sch = db_session.query(School).filter(School.name=="BD").first() db_session.query(Student).filter(Student.school_id == sch.id).delete() db_session.commit() db_session.close()
多对多的增删改查：
from sqlalchemy.ext.declarative import declarative_base Base = declarative_base() from sqlalchemy import Column, Integer, String, ForeignKey from sqlalchemy.orm import relationship class Girls(Base): __tablename__ = "girl" id = Column(Integer, primary_key=True) name = Column(String(32)) #创建关系 girl2boy = relationship("Boys",secondary="hotel",backref="boy2girl") class Boys(Base): __tablename__ = "boy" id = Column(Integer, primary_key=True) name = Column(String(32)) class Hotel(Base): __tablename__ = "hotel" id = Column(Integer, primary_key=True) girl_id = Column(Integer, ForeignKey("girl.id")) boy_id = Column(Integer, ForeignKey("boy.id")) from sqlalchemy import create_engine engine = create_engine("mysql+pymysql://root:@127.0.0.1:3306/day127?charset=utf8") Base.metadata.create_all(engine)
from sqlalchemy.orm import sessionmaker from M2M import engine Session = sessionmaker(engine) db_session = Session() # 1.通过Boy添加Girl和Hotel数据 relationship 反向 # boy = Boys(name="刘备") # boy.boy2girl = [Girls(name="孙尚香"),Girls(name="甘夫人")] # db_session.add(boy) # db_session.commit() # db_session.close() # 2.通过Girl添加 Boy 和 Hotel 数据 relationship 正向 # girl_obj = Girls(name="貂蝉",girl2boy=[Boys(name="吕布"),Boys(name="董卓")]) # db_session.add(girl_obj) # db_session.commit() # db_session.close() # 3.查询 relationship 正向 # g_list = db_session.query(Girls).all() # for girl in g_list: # for boy in girl.girl2boy: # print(girl.name,boy.name) # 4.查询 relationship 反向 # b_list = db_session.query(Boys).all() # for boy in b_list: # for girl in boy.boy2girl: # print(boy.name,girl.name)
更多操作：
# 高级版查询操作 from create_table import User, engine from sqlalchemy.orm import sessionmaker Session = sessionmaker(engine) db_session = Session() # 查询数据表操作 # and or # res = db_session.query(User).filter(User.id == 4 or User.name == "LBZ").all() # print(res[0].name,res) # # if False and True: # print("lihaile") # from sqlalchemy.sql import and_ , or_ # ret = db_session.query(User).filter(and_(User.id == 3, User.name == 'LBZ')).all() # print(ret) # ret = db_session.query(User).filter(or_(User.id == 4, User.name == 'LBZ')).all() # print(ret) # ret = db_session.query(User).filter_by(id=4,name="LBZ").all() # print(ret) # 查询数据 指定查询数据列 加入别名 # r2 = db_session.query(User.id.label("uid"),User.name.label("username")).first() # print(r2.uid,r2.username) # 字符串匹配方式筛选条件 复杂查询 # from sqlalchemy.sql import text # r6 = db_session.query(User).filter(text("id=:value and name=:name")).params(value=3, name='LBZ').first() # print(r6.name) # 原生SQL查询 # r7 = db_session.query(User).from_statement(text("SELECT * FROM User where name=:name")).params(name='LBZ').all() # 筛选查询列 # query的时候我们不再使用User ORM对象,而是使用User.name来对内容进行选取 # user_list = db_session.query(User.name).all() # print(user_list) # for row in user_list: # print(row.name) # 排序 : # user_list = db_session.query(User).order_by(User.id.asc()).all() # user_list = db_session.query(User).order_by(User.id.desc()).all() # for row in user_list: # print(row.name,row.id) # 其他查询条件 """ ret = session.query(User).filter_by(name='LBZ').all() ret = session.query(User).filter(User.id > 1, User.name == 'LBZ').all() ret = session.query(User).filter(User.id.between(1, 3), User.name == 'LBZ').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='LBZ'))).all() 子查询 from sqlalchemy import and_, or_ ret = session.query(User).filter(and_(User.id > 3, User.name == 'LBZ')).all() ret = session.query(User).filter(or_(User.id < 2, User.name == 'LBZ')).all() ret = session.query(User).filter( or_( User.id < 2, and_(User.name == 'LBZ', User.id > 3), User.extra != "" )).all() # select * from User where id<2 or (name="LBZ" 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() """ # ret = db_session.query(User).filter(User.id.between(1, 3)).all() # between 大于1小于3的 # print(ret) # ret = db_session.query(User).filter(User.id.in_([1,4])).all() # in_([1,3,4]) 只查询id等于1,4的 # ret = db_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 # print(ret) # from sqlalchemy.sql import and_, or_ # # ret = db_session.query(User).filter( # or_( # User.id < 2, # and_(User.name == 'LBZ', User.id > 3), # User.name != "" # )) # print(ret) # 关闭连接 db_session.close()
#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 - 1 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 - 2 # db_session.query(User).filter(User.id > 0).update({"age": User.age + 1}, synchronize_session="evaluate") # db_session.commit()
1.创建数据表
# ORM中的数据表是什么呢? # Object Relation Mapping # Object - Table 通过 Object 去操纵数据表 # 从而引出了我们的第一步创建数据表 - 创建Object # 1. 创建Object # class User(object): # pass # 2. 让Object与数据表产生某种关系 也就是让Object与数据表格式极度相似 # 导入官宣基础模型 from sqlalchemy.ext.declarative import declarative_base # 实例化官宣模型 - Base 就是 ORM 模型 Base = declarative_base() # 当前的这个Object继承了Base也就是代表了Object继承了ORM的模型 class User(Base): # 相当于 Django Models中的 Model # 为Table创建名称 __tablename__ = "user" # 创建ID数据字段 , 那么ID是不是一个数据列呢? 也就是说创建ID字段 == 创建ID数据列 from sqlalchemy import Column,Integer,String # id = Column(数据类型,索引,主键,外键,等等) # int == Integer id = Column(Integer,primary_key=True,autoincrement=True) # str == char(长度) == String(长度) name = Column(String(32),index=True) # 3.去数据库中创建数据表? or 先连接数据库? # 3.去连接数据库 创建数据引擎 from sqlalchemy import create_engine # 创建的数据库引擎 engine = create_engine("mysql+pymysql://root:DragonFire@127.0.0.1:3306/dragon?charset=utf8") # Base 自动检索所有继承Base的ORM 对象 并且创建所有的数据表 Base.metadata.create_all(engine)
2.增删改查操作
2.1.增加数据
#insert 为数据表增加数据 # insert One 增加一行数据 # insert into user(name) values ("DragonFire") # 在ORM中的操作: # 1.首先导入之间做好的ORM 对象 User from my_create_table import User # 2.使用Users ORM模型创建一条数据 user1 = User(name="DragonFire") # 数据已经创建完了,但是需要写入到数据库中啊,怎么写入呢? # 3.写入数据库: # 首先打开数据库会话 , 说白了就是创建了一个操纵数据库的窗口 # 导入 sqlalchemy.orm 中的 sessionmaker from sqlalchemy.orm import sessionmaker # 导入之前创建好的 create_engine from my_create_table import engine # 创建 sessionmaker 会话对象,将数据库引擎 engine 交给 sessionmaker Session = sessionmaker(engine) # 打开会话对象 Session db_session = Session() # 在db_session会话中添加一条 UserORM模型创建的数据 db_session.add(user1) # 使用 db_session 会话提交 , 这里的提交是指将db_session中的所有指令一次性提交 db_session.commit() # 当然也你也可很任性的提交多条数据 # 方法一: user2 = User(name="Dragon") user3 = User(name="Fire") db_session.add(user2) db_session.add(user3) db_session.commit() # 之前说过commit是将db_session中的所有指令一次性提交,现在的db_session中至少有两条指令user2和user3 db_session.close() #关闭会话 # 如果说你觉得方法一很麻烦,那么方法二一定非常非常适合你 # 方法二: user_list = [ User(name="Dragon1"), User(name="Dragon2"), User(name="Dragon3") ] db_session.add_all(user_list) db_session.commit() db_session.close()
2.2.查询数据
# ORM操作查询数据 # 有了刚才Insert增加数据的经验,那么查询之前的准备工作,就不用再重复了吧 # 回想一下刚才Insert时我们的操作 from my_create_table import User, engine from sqlalchemy.orm import sessionmaker Session = sessionmaker(engine) db_session = Session() # 1. select * from user 查询user表中的所有数据 # 语法是这样的 使用 db_session 会话 执行User表 query(User) 取出全部数据 all() user_all_list = db_session.query(User).all() print(user_all_list) # [<my_create_table.User object at 0x0000016D7C4BCDD8>] # 如何查看user_all_list其中的数据呢? 循环呗 for i in user_all_list: print(i.id, i.name) # ORM对象 直接使用调用属性的方法 拿出对应字段的值 db_session.close() #关闭会话 # 2. select * from user where id >= 20 # 语法是这样的 使用 db_session 会话 执行User表 query(User) 筛选内容User.id >=20 的数据全部取出 all() user_all_list = db_session.query(User).filter(User.id >= 20).all() print(user_all_list) for i in user_all_list: print(i.id, i.name) db_session.close() #关闭会话 # 3. 除了取出全部还可以只取出一条 user = db_session.query(User).filter(User.id >= 20).first() print(user.id, user.name) db_session.close() #关闭会话 # 4. 乌龙 之 忘了取出数据....... wulong1 = db_session.query(User).filter(User.id >= 20) print(wulong1) #SELECT user.id AS user_id, user.name AS user_name #FROM user #WHERE user.id >= %(id_1)s # Fuck我忘了取出数据了!!!!!!! 哎? wulong1给我显示了原生SQL语句,因祸得福了 wulong2 = db_session.query(User) print(wulong2) #SELECT user.id AS user_id, user.name AS user_name #FROM user # Fuck我又忘了取出数据了!!!!!!! 哎? wulong2给我显示了原生SQL语句,因祸得福了 db_session.close() #关闭会话
2.3.修改数据
# ORM更新数据 # 无论是更新还是删除,首先要做的事情,就应该是查询吧 # 根据之前原有的经验,接下来是不是要导入ORM对象了,是不是要创建db_session会话了 from my_create_table import User,engine from sqlalchemy.orm import sessionmaker Session = sessionmaker(engine) db_session = Session() # UPDATE user SET name="NBDragon" WHERE id=20 更新一条数据 # 语法是这样的 : # 使用 db_session 执行User表 query(User) 筛选 User.id = 20 的数据 filter(User.id == 20) # 将name字段的值改为NBDragon update({"name":"NBDragon"}) res = db_session.query(User).filter(User.id == 20).update({"name":"NBDragon"}) print(res) # 1 res就是我们当前这句更新语句所更新的行数 # 注意注意注意 # 这里一定要将db_session中的执行语句进行提交,因为你这是要对数据中的数据进行操作 # 数据库中 增 改 删 都是操作,也就是说执行以上三种操作的时候一定要commit db_session.commit() db_session.close() #关闭会话 # 更新多条 res = db_session.query(User).filter(User.id <= 20).update({"name":"NBDragon"}) print(res) # 6 res就是我们当前这句更新语句所更新的行数 db_session.commit() db_session.close() #关闭会话
2.4.删除数据
# ORM 删除一条多条数据 # 老规矩 # 导入 ORM 创建会话 from my_create_table import User,engine from sqlalchemy.orm import sessionmaker Session = sessionmaker(engine) db_session = Session() # DELETE FROM `user` WHERE id=20 res = db_session.query(User).filter(User.id==20).delete() print(res) # 是删除操作吧,没错吧,那你想什么呢?commit吧 db_session.commit() db_session.close() #关闭会话
2.5.搞基!高级版查询操作
# 高级版查询操作,厉害了哦 #老规矩 from my_create_table import User,engine from sqlalchemy.orm import sessionmaker Session = sessionmaker(engine) db_session = Session() # 查询数据表操作 # and or from sqlalchemy.sql import and_ , or_ ret = db_session.query(User).filter(and_(User.id > 3, User.name == 'DragonFire')).all() ret = db_session.query(User).filter(or_(User.id < 2, User.name == 'DragonFire')).all() # 查询所有数据 r1 = db_session.query(User).all() # 查询数据 指定查询数据列 加入别名 r2 = db_session.query(User.name.label('username'), User.id).first() print(r2.id,r2.username) # 15 NBDragon # 表达式筛选条件 r3 = db_session.query(User).filter(User.name == "DragonFire").all() # 原生SQL筛选条件 r4 = db_session.query(User).filter_by(name='DragonFire').all() r5 = db_session.query(User).filter_by(name='DragonFire').first() # 字符串匹配方式筛选条件 并使用 order_by进行排序 r6 = db_session.query(User).filter(text("id<:value and name=:name")).params(value=224, name='DragonFire').order_by(User.id).all() #原生SQL查询 r7 = db_session.query(User).from_statement(text("SELECT * FROM User where name=:name")).params(name='DragonFire').all() # 筛选查询列 # query的时候我们不在使用User ORM对象,而是使用User.name来对内容进行选取 user_list = db_session.query(User.name).all() print(user_list) for row in user_list: print(row.name) # 别名映射 name as nick user_list = db_session.query(User.name.label("nick")).all() print(user_list) for row in user_list: print(row.nick) # 这里要写别名了 # 筛选条件格式 user_list = db_session.query(User).filter(User.name == "DragonFire").all() user_list = db_session.query(User).filter(User.name == "DragonFire").first() user_list = db_session.query(User).filter_by(name="DragonFire").first() for row in user_list: print(row.nick) # 复杂查询 from sqlalchemy.sql import text user_list = db_session.query(User).filter(text("id<:value and name=:name")).params(value=3,name="DragonFire") # 查询语句 from sqlalchemy.sql import text user_list = db_session.query(User).filter(text("select * from User id<:value and name=:name")).params(value=3,name="DragonFire") # 排序 : user_list = db_session.query(User).order_by(User.id).all() user_list = db_session.query(User).order_by(User.id.desc()).all() for row in user_list: print(row.name,row.id) #其他查询条件 """ 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() """ # 关闭连接 db_session.close()
2.6.高级修改数据操作
#高级版更新操作 from my_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 - 1 db_session.query(User).filter(User.id > 0).update({User.name: User.name + "099"}, synchronize_session=False) #在原有值基础上添加 - 2 db_session.query(User).filter(User.id > 0).update({"age": User.age + 1}, synchronize_session="evaluate") db_session.commit()
3.一对多的操作 : ForeignKey
3.1.创建数据表及关系relationship:
from sqlalchemy.ext.declarative import declarative_base Base = declarative_base() # 这次我们要多导入一个 ForeignKey 字段了,外键关联对了 from sqlalchemy import Column,Integer,String,ForeignKey # 还要从orm 中导入一个 relationship 关系映射 from sqlalchemy.orm import relationship class ClassTable(Base): __tablename__="classtable" id = Column(Integer,primary_key=True) name = Column(String(32),index=True) class Student(Base): __tablename__="student" id=Column(Integer,primary_key=True) name = Column(String(32),index=True) # 关联字段,让class_id 与 class 的 id 进行关联,主外键关系(这里的ForeignKey一定要是表名.id不是对象名) class_id = Column(Integer,ForeignKey("classtable.id")) # 将student 与 classtable 创建关系 这个不是字段,只是关系,backref是反向关联的关键字 to_class = relationship("ClassTable",backref = "stu2class") from sqlalchemy import create_engine engine = create_engine("mysql+pymysql://root:DragonFire@127.0.0.1:3306/dragon?charset=utf8") Base.metadata.create_all(engine)
3.2.基于relationship增加数据
from my_ForeignKey import Student, ClassTable,engine # 创建连接 from sqlalchemy.orm import sessionmaker # 创建数据表操作对象 sessionmaker DB_session = sessionmaker(engine) db_session = DB_session() # 增加数据 # 1.简单增加数据 # 添加两个班级: # db_session.add_all([ # ClassTable(name="OldBoyS1"), # ClassTable(name="OldBoyS2") # ]) # db_session.commit() # 添加一个学生 DragonFire 班级是 OldBoyS1 # 查询要添加到的班级 # class_obj = db_session.query(ClassTable).filter(ClassTable.name == "OldBoyS1").first() # 创建学生 # stu = Student(name="DragonFire",class_id = class_obj.id) # db_session.add(stu) # db_session.commit() # 2. relationship版 添加数据 # 通过关系列 to_class 可以做到两件事 # 第一件事 在ClassTable表中添加一条数据 # 第二件事 在Student表中添加一条数据并将刚刚添加的ClassTable的数据id填写在Student的class_id中 # stu_cla = Student(name="DragonFire",to_class=ClassTable(name="OldBoyS1")) # print(stu_cla.name,stu_cla.class_id) # db_session.add(stu_cla) # db_session.commit() # 3.relationship版 反向添加数据 # 首先建立ClassTable数据 class_obj = ClassTable(name="OldBoyS2") # 通过class_obj中的反向关联字段backref - stu2class # 向 Student 数据表中添加 2条数据 并将 2条数据的class_id 写成 class_obj的id # class_obj.stu2class = [Student(name="BMW"),Student(name="Audi")] # db_session.add(class_obj) # db_session.commit() # 关闭连接 db_session.close()
3.3.基于relationship查询数据
from my_ForeignKey import Student, ClassTable,engine from sqlalchemy.orm import sessionmaker DB_session = sessionmaker(engine) db_session = DB_session() # 1.查询所有数据,并显示班级名称,连表查询 student_list = db_session.query(Student).all() for row in student_list: # row.to_class.name 通过Student对象中的关系字段relationship to_class 获取关联 ClassTable中的name print(row.name,row.to_class.name,row.class_id) # 2.反向查询 class_list = db_session.query(ClassTable).all() for row in class_list: for row2 in row.stu2class: print(row.name,row2.name) # row.stu2class 通过 backref 中的 stu2class 反向关联到 Student 表中根据ID获取name db_session.close()
3.4.更新数据
from my_ForeignKey import Student, ClassTable,engine from sqlalchemy.orm import sessionmaker DB_session = sessionmaker(engine) db_session = DB_session() # 更新 class_info = db_session.query(ClassTable).filter(ClassTable.name=="OldBoyS1").first() db_session.query(Student).filter(Student.class_id == class_info.id).update({"name":"NBDragon"}) db_session.commit() db_session.close()
3.5.删除数据
from my_ForeignKey import Student, ClassTable,engine from sqlalchemy.orm import sessionmaker DB_session = sessionmaker(engine) db_session = DB_session() # 删除 class_info = db_session.query(ClassTable).filter(ClassTable.name=="OldBoyS1").first() db_session.query(Student).filter(Student.class_id == class_info.id).delete() db_session.commit() db_session.close()
4.多对多 : ManyToMany
4.1.创建表及关系
from sqlalchemy.ext.declarative import declarative_base Base = declarative_base() from sqlalchemy import Column,Integer,String,ForeignKey from sqlalchemy.orm import relationship class Hotel(Base): __tablename__="hotel" id=Column(Integer,primary_key=True) girl_id = Column(Integer,ForeignKey("girl.id")) boy_id = Column(Integer,ForeignKey("boy.id")) class Girl(Base): __tablename__="girl" id=Column(Integer,primary_key=True) name = Column(String(32),index=True) #创建关系 boys = relationship("Boy",secondary="hotel",backref="girl2boy") class Boy(Base): __tablename__="boy" id=Column(Integer,primary_key=True) name = Column(String(32),index=True) from sqlalchemy import create_engine engine = create_engine("mysql+pymysql://root:DragonFire@127.0.0.1:3306/dragon?charset=utf8") Base.metadata.create_all(engine)
4.2.基于relationship增加数据
from my_M2M import Girl,Boy,Hotel,engine # 创建连接 from sqlalchemy.orm import sessionmaker # 创建数据表操作对象 sessionmaker DB_session = sessionmaker(engine) db_session = DB_session() # 1.通过Boy添加Girl和Hotel数据 boy = Boy(name="DragonFire") boy.girl2boy = [Girl(name="赵丽颖"),Girl(name="Angelababy")] db_session.add(boy) db_session.commit() # 2.通过Girl添加Boy和Hotel数据 girl = Girl(name="珊珊") girl.boys = [Boy(name="Dragon")] db_session.add(girl) db_session.commit()
4.3.基于relationship查询数据
from my_M2M import Girl,Boy,Hotel,engine # 创建连接 from sqlalchemy.orm import sessionmaker # 创建数据表操作对象 sessionmaker DB_session = sessionmaker(engine) db_session = DB_session() # 1.通过Boy查询约会过的所有Girl hotel = db_session.query(Boy).all() for row in hotel: for row2 in row.girl2boy: print(row.name,row2.name) # 2.通过Girl查询约会过的所有Boy hotel = db_session.query(Girl).all() for row in hotel: for row2 in row.boys: print(row.name,row2.name)
