每个项目都离不开数据库，所以要是打算用Flask写一个程序，自然也离不开flask-sqlalchemy。作为一个mysql DBA，当然会首选MySQL作为程序的数据库，毕竟我擅长于此。那么就来总结下，怎么用flask-sqlalchemy来玩转MySQL吧。
安装命令pip install mysql-python pip install flask-sqlalchemy
相关示例Python代码 # 文件名hello.py from flask import Flask from flask_sqlalchemy import SQLAlchemy app = Flask(__name__) app.config['SECRET_KEY'] = 'Fianna' app.config['SQLALCHEMY_DATABASE_URI'] = 'mysql://user:password@host:port/dbname' app.config['SQLALCHEMY_TRACK_MODIFICATIONS'] = True db = SQLAlchemy(app) class Role(db.Model): __tablename__ = 'roles' id = db.Column(db.Integer, nullable=False, primary_key=True, autoincrement=True) name = db.Column(db.String(16), nullable=False, server_default='', unique=True) def __repr__(self): return '<Role %r>' % self.name class User(db.Model): __tablename__ = 'users' id = db.Column(db.Integer, nullable=False, primary_key=True, autoincrement=True) username = db.Column(db.String(32), nullable=False, unique=True, server_default='', index=True) role_id = db.Column(db.Integer, nullable=False, server_default='0') def __repr__(self): return '<User %r,Role id %r>' %(self.username,self.role_id) 一、连接数据库 app.config['SQLALCHEMY_DATABASE_URI'] = 'mysql://user:password@host:port/dbname' 二、创建所有表python hello.py shell >>> from hello import db,Role,User >>> db.create_all()
三、删除所有表python hello.py shell >>>from hello import db,Role,User >>>db.drop_all()
四、插入行 # 插入单行 python hello.py shell >>>from hello import db,Role,User >>>db.session.add(Role(name='Admin')) >>>db.session.commit() >>>db.session.add(Role(name='Moderator')) >>>db.session.add(Role(name='User')) >>>db.session.commit() # 插入多行 python hello.py shell >>>from hello import db,Role,User >>>db.session.add_all([User(username='john',role_id=1),User(username='susan',role_id=3),User(username='david',role_id=3)]) >>>db.session.commit() 五、更新行python hello.py shell >>>from hello import db,Role,User >>>admin = Role.query.filter_by(name='Admin').first() >>>admin.name='Administrator' >>>db.session.commit()
六、删除行python hello.py shell >>>from hello import db,Role,User >>>mod = Role.query.filter_by(name='Moderator').first() >>>db.session.delete(mod) >>>db.session.commit()
七、查询表查询表中全部数据
# 注意，此处的查询结果完全取决于代码示例中的 # def __repr__(self) # 这段函数，请各位小主们，好好斟酌下～ python hello.py shell >>>from hello import db,Role,User >>>Role.query.all() [<Role u'Administrator'>, <Role u'User'>] >>>User.query.all() [<User u'john',Role id 1L>, <User u'susan',Role id 3L>, <User u'david',Role id 3L>]按照一个条件过滤数据记录(where)
python hello.py shell >>>from hello import db,Role,User >>>Role.query.filter_by(name='Administrator').first() <Role u'Administrator'> >>>User.query.filter_by(role_id=3).all() [<User u'susan',Role id 3L>, <User u'david',Role id 3L>] >>>User.query.filter_by(role_id=3).first() <User u'susan',Role id 3L>按照两个条件过滤数据记录(where and)
python hello.py shell >>>from hello import db,Role,User >>>User.query.filter_by(role_id=3,username='susan').first() <User u'susan',Role id 3L> >>>User.query.filter_by(role_id=3,username='susan').all() [<User u'susan',Role id 3L>]聚合(count)
python hello.py shell >>>from hello import db,Role,User >>>User.query.filter_by(role_id=3,username='susan').count() 1L >>>User.query.filter_by(role_id=3).count() 2L >>>User.query.count() 3L
求和(sum)
python hello.py shell >>>from hello import db,Role,User >>>from sqlalchemy.sql import func >>>User.query.with_entities(func.sum(User.id)).all() [(Decimal('6'),)] >>>User.query.with_entities(func.sum(User.role_id)).all() [(Decimal('7'),)]平均数(avg)
python hello.py shell >>>from hello import db,Role,User >>>from sqlalchemy.sql import func >>>User.query.with_entities(func.avg(User.role_id)).all() [(Decimal('2.3333'),)] >>>User.query.with_entities(func.avg(User.id)).all() [(Decimal('2.0000'),)]排序(order by)
python hello.py shell >>>from hello import db,Role,User # 升序(asc) >>>User.query.order_by(User.role_id).all() [<User u'john',Role id 1L>, <User u'susan',Role id 3L>, <User u'david',Role id 3L>] # 降序(desc) >>>User.query.order_by(User.role_id.desc()).all() [<User u'susan',Role id 3L>, <User u'david',Role id 3L>, <User u'john',Role id 1L>]分组(group by)
python hello.py shell >>>from hello import db,Role,User >>>User.query.group_by(User.role_id).all() [<User u'john',Role id 1L>, <User u'susan',Role id 3L>]限制(limit)
python hello.py shell >>>from hello import db,Role,User >>>User.query.all() [<User u'john',Role id 1L>, <User u'susan',Role id 3L>, <User u'david',Role id 3L>] # limit 1 >>>User.query.limit(1).all() [<User u'john',Role id 1L>] # limit 2,1 >>>User.query.limit(1).offset(2).all() [<User u'david',Role id 3L>] >>>User.query.filter_by(role_id=3).all() [<User u'susan',Role id 3L>, <User u'david',Role id 3L>] # limit 1 >>>User.query.filter_by(role_id=3).limit(1).all() [<User u'susan',Role id 3L>] # limit 1,1 >>>User.query.filter_by(role_id=3).limit(1).offset(1).all() [<User u'david',Role id 3L>] 八、将Flask-SQLAlchemy的查询语句转换为SQL python hello.py shell >>>from hello import db,Role,User >>>User.query.all() [<User u'john',Role id 1L>, <User u'susan',Role id 3L>, <User u'david',Role id 3L>] >>>str(User.query) 'SELECT users.id AS users_id, users.username AS users_username, users.role_id AS users_role_id \nFROM users' >>>User.query.limit(1).all() [<User u'john',Role id 1L>] >>>str(User.query.limit(1)) 'SELECT users.id AS users_id, users.username AS users_username, users.role_id AS users_role_id \nFROM users \n LIMIT %s' >>>User.query.limit(1).offset(2).all() [<User u'david',Role id 3L>] >>>str(User.query.limit(1).offset(2)) 'SELECT users.id AS users_id, users.username AS users_username, users.role_id AS users_role_id \nFROM users \n LIMIT %s, %s'本文示例参考文档：《Flask web开发》