（1）安装
pip install flask_sqlalchemy
（2）数据库连接
from flask import Flask # 1.导入 from flask_sqlalchemy import SQLAlchemy app = Flask(__name__) #2.定义要连接的数据库 DB_URI = "mysql+pymysql://root:123456@127.0.0.1:3306/learn_sqlalchemy?charset=utf8" #3.添加到到配置中 app.config['SQLALCHEMY_DATABASE_URI'] = DB_URI
app.config['SQLALCHEMY_TRACK_MODIFICATIONS'] =False # 4.实例化一个对象，将app传进去 db = SQLAlchemy(app) @app.route('/') def hello_world(): return 'Hello World!' if __name__ == '__main__': app.run()
（3）创建表
from flask import Flask from flask_sqlalchemy import SQLAlchemy app = Flask(__name__) DB_URI = "mysql+pymysql://root:123456@127.0.0.1:3306/learn_sqlalchemy?charset=utf8" app.config['SQLALCHEMY_DATABASE_URI'] = DB_URI app.config['SQLALCHEMY_TRACK_MODIFICATIONS'] = False db = SQLAlchemy(app) class User(db.Model): __tablename__ = 'user' id = db.Column(db.Integer,primary_key=True,autoincrement=True) username = db.Column(db.String(50),nullable=False) class Article(db.Model): __tablename__ = "article" id = db.Column(db.Integer, primary_key=True, autoincrement=True) title = db.Column(db.String(50), nullable=False) uid = db.Column(db.Integer,db.ForeignKey("user.id")) author = db.relationship("User",backref='article') db.drop_all() #删除表 db.create_all() #创建表 @app.route('/') def hello_world(): return 'Hello World!' if __name__ == '__main__': app.run()
（4）添加数据
from flask import Flask from flask_sqlalchemy import SQLAlchemy app = Flask(__name__) DB_URI = "mysql+pymysql://root:123456@127.0.0.1:3306/learn_sqlalchemy?charset=utf8" app.config['SQLALCHEMY_DATABASE_URI'] = DB_URI app.config['SQLALCHEMY_TRACK_MODIFICATIONS'] = False db = SQLAlchemy(app) class User(db.Model): __tablename__ = 'user' id = db.Column(db.Integer,primary_key=True,autoincrement=True) username = db.Column(db.String(50),nullable=False) class Article(db.Model): __tablename__ = "article" id = db.Column(db.Integer, primary_key=True, autoincrement=True) title = db.Column(db.String(50), nullable=False) uid = db.Column(db.Integer,db.ForeignKey("user.id")) author = db.relationship("User",backref='article') # db.drop_all() #删除表 # db.create_all() #创建表 #添加数据 user = User(username='derek') article = Article(title='今天5/27号') article.author = user db.session.add(article) db.session.commit() @app.route('/') def hello_world(): return 'Hello World!' if __name__ == '__main__': app.run()
（5）查看、修改和删除
from flask import Flask from flask_sqlalchemy import SQLAlchemy app = Flask(__name__) DB_URI = "mysql+pymysql://root:123456@127.0.0.1:3306/learn_sqlalchemy?charset=utf8" app.config['SQLALCHEMY_DATABASE_URI'] = DB_URI app.config['SQLALCHEMY_TRACK_MODIFICATIONS'] = False db = SQLAlchemy(app) class User(db.Model): __tablename__ = 'user' id = db.Column(db.Integer,primary_key=True,autoincrement=True) username = db.Column(db.String(50),nullable=False) def __repr__(self): return "<username:%s>"%self.username class Article(db.Model): __tablename__ = "article" id = db.Column(db.Integer, primary_key=True, autoincrement=True) title = db.Column(db.String(50), nullable=False) uid = db.Column(db.Integer,db.ForeignKey("user.id")) author = db.relationship("User",backref='article') # db.drop_all() #删除表 # db.create_all() #创建表 # 1.添加数据 # user = User(username='derek') # article = Article(title='今天5/27号') # article.author = user # # db.session.add(article) # db.session.commit() # 2.查询数据 # users=User.query.all() # print(users) # 3.修改数据,先查找出来再修改 # user = User.query.filter(User.username=='derek').first() # user.username = 'jack' # db.session.commit() # 4.删除数据 user = User.query.filter(User.username=='jack').first() db.session.delete(user) db.session.commit() @app.route('/') def hello_world(): return 'Hello World!' if __name__ == '__main__': app.run()
SQLAlchemy 没有 Django 的 Models 好用
我在这里官宣辟谣一下啊, Models 紧紧只是配置和使用比较简单(这特么就是废话),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
当然了,无论是使用什么ORM框架,都是为了方便不熟练数据库的同学使用的,我个人还是比较推崇原生 SQL ,也建议每位同学攻克 SQL 的难关
废话不多说,我们来看一下 SQLAlchemy 如何使用:
单表操作:
1.创建
创建基类和第一张数据表
2.增删改查相关操作:
增删改查3.搞基高几高技告急膏剂高集高吉高级版查询操作
1 from CreateDB import Users, School 2 3 # 1. 创建一个用户添加到数据库 4 # 创建连接 5 from sqlalchemy import create_engine 6 from sqlalchemy.orm import sessionmaker 7 engine = create_engine("mysql+pymysql://root:DragonFire@127.0.0.1:3306/dragon?charset=utf8", 8 ) 9 10 # 创建数据表操作对象 sessionmaker 11 DB_session = sessionmaker(engine) 12 db_session = DB_session() 13 14 # 查询数据表操作 15 """ 16 r1 = session.query(Users).all() 17 r2 = session.query(Users.name.label('xx'), Users.age).all() 18 r3 = session.query(Users).filter(Users.name == "alex").all() 19 r4 = session.query(Users).filter_by(name='alex').all() 20 r5 = session.query(Users).filter_by(name='alex').first() 21 r6 = session.query(Users).filter(text("id<:value and name=:name")).params(value=224, name='fred').order_by(Users.id).all() 22 r7 = session.query(Users).from_statement(text("SELECT * FROM users where name=:name")).params(name='ed').all() 23 """ 24 # 筛选查询列 25 # user_list = db_session.query(Users.name).all() 26 # print(user_list) # [('alexDSB',), ('zhangsan',)] 虽然看到的是元祖,但是依然可以通过对象打点儿调用属性 27 # for row in user_list: 28 # print(row.name) 29 30 # 别名映射 name as nick 31 # user_list = db_session.query(Users.name.label("nick")).all() 32 # print(user_list) # [('alexDSB',), ('zhangsan',)] 虽然看到的是元祖,但是依然可以通过对象打点儿调用属性 33 # for row in user_list: 34 # print(row.nick) # 这里要写别名了 35 36 # 筛选条件格式 37 # user_list = db_session.query(Users).filter(Users.name == "alexDSB").all() 38 # user_list = db_session.query(Users).filter(Users.name == "alexDSB").first() 39 # user_list = db_session.query(Users).filter_by(name="alexDSB").first() 40 # for row in user_list: 41 # print(row.nick) 42 43 # 复杂查询 44 # from sqlalchemy.sql import text 45 # user_list = db_session.query(Users).filter(text("id<:value and name=:name")).params(value=3,name="alexDSB") 46 47 # 查询语句 48 # from sqlalchemy.sql import text 49 # user_list = db_session.query(Users).filter(text("select * from users id<:value and name=:name")).params(value=3,name="alexDSB") 50 51 # 排序 : 52 # user_list = db_session.query(Users).order_by(Users.id).all() 53 # user_list = db_session.query(Users).order_by(Users.id.desc()).all() 54 # for row in user_list: 55 # print(row.name,row.id) 56 57 #其他查询条件 58 """ 59 ret = session.query(Users).filter_by(name='alex').all() 60 ret = session.query(Users).filter(Users.id > 1, Users.name == 'eric').all() 61 ret = session.query(Users).filter(Users.id.between(1, 3), Users.name == 'eric').all() # between 大于1小于3的 62 ret = session.query(Users).filter(Users.id.in_([1,3,4])).all() # in_([1,3,4]) 只查询id等于1,3,4的 63 ret = session.query(Users).filter(~Users.id.in_([1,3,4])).all() # ~xxxx.in_([1,3,4]) 查询不等于1,3,4的 64 ret = session.query(Users).filter(Users.id.in_(session.query(Users.id).filter_by(name='eric'))).all() 子查询 65 from sqlalchemy import and_, or_ 66 ret = session.query(Users).filter(and_(Users.id > 3, Users.name == 'eric')).all() 67 ret = session.query(Users).filter(or_(Users.id < 2, Users.name == 'eric')).all() 68 ret = session.query(Users).filter( 69 or_( 70 Users.id < 2, 71 and_(Users.name == 'eric', Users.id > 3), 72 Users.extra != "" 73 )).all() 74 # select * from users where id<2 or (name="eric" and id>3) or extra != "" 75 """ 76 77 # 关闭连接 78 db_session.close()
4.高级版更新操作
高级版更新操作5.扩展内容
排序分组选取通配符一对多的操作 : ForeignKey
1.创建表:
from sqlalchemy import create_engine from sqlalchemy.ext.declarative import declarative_base from sqlalchemy import Column, Integer, String, ForeignKey from sqlalchemy.orm import relationship #创建基类,相当于Django中的 models.Model,被各个数据表类所继承 Base = declarative_base() # ##################### 多表示例 ######################### # 创建一张数据表 class Author(Base): __tablename__ = 'author' id = Column(Integer, primary_key=True) name = Column(String(32), index=True) # 创建另一张数据表 class Book(Base): __tablename__ = 'book' id = Column(Integer, primary_key=True) name = Column(String(32), index=True) author_id = Column(Integer,ForeignKey("author.id")) # relationshi 不会单独生成字段 ,只用于增加查询操作 user = relationship("Author",backref="author2book") # backref 反向查找的名字 # 创建数据库链接 engine = create_engine( "mysql+pymysql://root:DragonFire@localhost:3306/dragon?charset=utf8", max_overflow=0, # 超过连接池大小外最多创建的连接 pool_size=5, # 连接池大小 pool_timeout=30, # 池中没有线程最多等待的时间，否则报错 pool_recycle=-1 # 多久之后对线程池中的线程进行一次连接的回收（重置） ) # 通过Base.metadata找到所有继承 Base 的数据表class Base.metadata.create_all(engine)
2.增删改查
1 from SQLAlchemy_ready.ss2_ForeignKey_relationship import Author, Book 2 3 # 1. 创建一个用户添加到数据库 4 # 创建连接 5 from sqlalchemy import create_engine 6 from sqlalchemy.orm import sessionmaker 7 engine = create_engine("mysql+pymysql://root:DragonFire@127.0.0.1:3306/dragon?charset=utf8", 8 ) 9 10 # 创建数据表操作对象 sessionmaker 11 DB_session = sessionmaker(engine) 12 db_session = DB_session() 13 14 # 1.增加 操作数据表 15 # 添加两个作者: 16 # db_session.add_all([ 17 # Author(name="alex"), 18 # Author(name="yinwangba") 19 # ]) 20 # db_session.commit() 21 # 添加一本书 jinpingmei 作者是 yinwangba 22 # author = db_session.query(Author).filter(Author.name == "yinwangba").first() 23 # db_session.add(Book(name="jinpingmei",author_id=author.id)) 24 # db_session.commit() 25 26 # 2.查询所有数据,并显示作者名称,连表查询 27 # book_list = db_session.query(Book).all() 28 # for row in book_list: 29 # print(row.name,row.author_id) 30 31 # book_list = db_session.query(Book.name.label("bname"),Author.name.label ("aname")).join(Author,Book.author_id == Author.id,isouter=True).all() 32 # print(book_list) 33 # for row in book_list: 34 # print(row.aname,row.bname) 35 36 # 查询之relationship 快速连表 37 # 创建表的时候加入 relationship 38 #普通版添加 39 # obj = Author(name="yinwangba") 40 # db_session.add(obj) 41 # db_session.commit() 42 # print(obj.id,obj.name) 43 # 44 # obj_book = Book(name="jinpingmei",author_id=obj.id) 45 # db_session.add(obj_book) 46 # db_session.commit() 47 # obj = Author(name="yinwangba") 48 49 # relationship版 添加 50 # bobj = Book(name="jinpingmei",user=Author(name="yinwangba")) 51 # db_session.add(bobj) 52 # db_session.commit() 53 54 # 查询之relationship 快速连表 55 # book_list = db_session.query(Book).all() 56 # for row in book_list: 57 # print(row.name,row.user.name) 58 59 # 查询作者的所有书籍 60 # obj = db_session.query(Author).filter(Author.name=="yinwangba").first() 61 # print(obj.author2book) 62 63 # 反向字段添加 64 # author_obj = Author(name="alex") 65 # author_obj.author2book = [Book(name="儒林外史之银林大战"),Book(name="邻家小妹妹")] 66 # db_session.add(author_obj) 67 # db_session.commit() 68 69 # 关闭连接 70 db_session.close()
多对多 : ManyToMany
1.创建表
1 import datetime 2 from sqlalchemy import create_engine 3 from sqlalchemy.ext.declarative import declarative_base 4 from sqlalchemy import Column, Integer, String, Text, ForeignKey, DateTime, UniqueConstraint, Index 5 from sqlalchemy.orm import relationship 6 7 #创建基类,相当于Django中的 models.Model,被各个数据表类所继承 8 Base = declarative_base() 9 10 # 创建第三张表 Boys and Girls 11 class Hotel(Base): 12 __tablename__ = "hotel" 13 14 id = Column(Integer,primary_key=True) 15 boy_id = Column(Integer,ForeignKey("boys.id")) 16 girl_id = Column(Integer,ForeignKey("girls.id")) 17 18 # 创建一张数据表 19 class Boys(Base): 20 __tablename__ = 'boys' 21 22 id = Column(Integer, primary_key=True) 23 name = Column(String(32), index=True) 24 25 # 创建于酒店的关系 26 girls = relationship("Girls",secondary="hotel",backref="boys") 27 28 # 创建另一张数据表 29 class Girls(Base): 30 __tablename__ = "girls" 31 32 id = Column(Integer,primary_key=True,autoincrement=True) 33 name = Column(String(32),index =True) 34 35 # 创建于酒店的关系 36 # boy = relationship("Boys",secondary="hotel",backref="toHotel") 37 38 39 40 41 42 43 44 45 46 # 创建数据库链接 47 engine = create_engine( 48 "mysql+pymysql://root:DragonFire@localhost:3306/dragon?charset=utf8", 49 max_overflow=0, # 超过连接池大小外最多创建的连接 50 pool_size=5, # 连接池大小 51 pool_timeout=30, # 池中没有线程最多等待的时间，否则报错 52 pool_recycle=-1 # 多久之后对线程池中的线程进行一次连接的回收（重置） 53 ) 54 55 # 通过Base.metadata找到所有继承 Base 的数据表class 56 Base.metadata.create_all(engine) 57 58 59 # SQLAlchemy数据表进行修改后,无法直接进行更新,只能删除表后进行操作,重新进行操作, 60 # 但Flask-SQLAlchemy + Flask-migrate + Flask-script 就可以实现 Django 的数据迁移 MakeMigration migrate 61 62 #
2.操作
1 from SQLAlchemy_ready.ss4_M2M import Girls, Boys,Hotel 2 3 # 1. 创建一个用户添加到数据库 4 # 创建连接 5 from sqlalchemy import create_engine 6 from sqlalchemy.orm import sessionmaker 7 engine = create_engine("mysql+pymysql://root:DragonFire@127.0.0.1:3306/dragon?charset=utf8") 8 9 10 # 创建数据表操作对象 sessionmaker 11 DB_session = sessionmaker(engine) 12 db_session = DB_session() 13 14 # 1.增加 操作数据表 15 # boy = Boys(name="jinwangba") 16 # boy.girls = [Girls(name="fengjie"),Girls(name="juaner")] 17 # db_session.add(boy) 18 # db_session.commit() 19 20 # 2.查询 21 # 使用relationship正向查询 22 # boy = db_session.query(Boys).first() 23 # print(boy.name,boy.girls[0].name) 24 25 # 使用relationship反向查询 26 # girls = db_session.query(Girls).first() 27 # print(girls.boys[0].name , girls.name) 28 29 30 # 关闭连接 31 db_session.close()
https://www.cnblogs.com/wupeiqi/articles/8259356.html