Flask-SQLAlchemy的使用

  1. 初始化

    • 安装sqlalchemy

      $ pip install flask-sqlalchemy``` 
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      * 初始化:		
      ```		
      # 导入包
      from flask.ext.sqlalchemy import SQLAlcheymy
      basedir = os.path.abspath(os.path.dirname(__file__))
      app = Flask(__name__)
      # 配置数据库路径
      app.config['SQLALCHEMY_DATABASE_URI'] =\
      	'sqlite:///'+os.path.join(basedir,'data.sqlite')
      app.config(['SQLALCHEMY_COMMIT_ON_TEARDOWN']) = True
      # 初始
      db = SQLAlchemy(app)

  2. 模型管理

  • 建立模型 
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class Role(db.Model):
	__tablename__ = 'roles'  # 自定义表名
	id = db.Column(db.Integer, primary_key=True)  # primary_key 主键
	name = db.Column(db.String(64), unique=True)  # unique 唯一
	def __repr__(self):
		return '<Role %r>' % self.name
class User(db.Model):= 'users'
	id = db.Column(db.Integer, primary_key=True)
	username = db.Column(db.String(64), unique=True, index=True) # index索引,有助于数据查询
	def __repr__(self):
		return '<User % __tablename__ r>' % self.username
```		
		
* 关系示例		
one-to-many示例:
```		
class Role(db.Model):
	# ...
	users = db.relationship('User', backref='role')
class User(db.Model):= 'users'
	# ..
	role_id = db.Column(db.Integer, db.ForeignKey('roles.id'))
```	
one-to-one示例:		
```		
class Role(db.Model):
	# ...
	user = db.relationship('User', backref='role', uselist=Flase) # 添加uselist为False
class User(db.Model):= 'users'
	# ..
	role_id = db.Column(db.Integer, db.ForeignKey('roles.id'))
```	
many-to-many示例:		
```		
# 关系定义需要先于model		
registrations = db.Table('registrations',
	db.Column('student_id', db.Integer, db.ForeignKey('students.id')),
	db.Column('class_id',db.Integer, db.ForeignKey('classes.id')))
class Student(db.Model):
	id = db.Column(db.Integer, primary_key=True)
	name = db.Column(db.String)
	classes = db.relationship('Class',
								secondary=registrations,
								backref=db.backref('students',lazy='dynamic'),
								lazy='dynamic')
class Class(db.Model):
	id = db.Column(db.Integer, primary_key=True)
	name = db.Column(db.String)

self many-to-many示例: 

class Follow(db.Model):
    __tablename__ = 'follows'
    follower_id = db.Column(db.Integer, db.ForeignKey('users.id'),
                            primary_key=True)
    followed_id = db.Column(db.Integer, db.ForeignKey('users.id'),
                            primary_key=True)
    timestamp = db.Column(db.DateTime, default=datetime.utcnow)

class User(UserMixin, db.Model): 
    # ...
    followed = db.relationship('Follow',
                               foreign_keys=[Follow.follower_id],
                               backref=db.backref('follower', lazy='joined'),
                               lazy='dynamic',
                               cascade='all, delete-orphan')
    followers = db.relationship('Follow',
                                foreign_keys=[Follow.followed_id],
                                backref=db.backref('followed', lazy='joined'),
                                lazy='dynamic',
                                cascade='all, delete-orphan')

UserMixin是什么鬼