Flask web minimalist tutorial (III) - Sqlalchemy (part a)

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One 、ORM Model design

stay MTV Architecture ,M Express Model The layer is responsible for interacting with the database ,ORM(Object Relational Mapping) Object relational mapping can map specific models to tables in the database one by one , The attributes of the model object correspond to the fields of the database table one by one ; Through the operation of the model to achieve the operation of the database table

ORM Important characteristics of ：

• Based on object-oriented programming idea
• Hardly write SQL, Improve development efficiency
• Support multiple types of database switching

SQLAlchemy

SQLAlchemy It's one that provides SQL Toolkit and object relation mapping （ORM） Third party libraries of tools ,Flask The framework itself does not ORM Functional , Therefore, it is necessary to use Flask-SQLAlchemy Extend to achieve ORM, About Flask-SQLAlchemy You can refer to Official documents

Flask Of ORM The extension needs to be installed separately , But it needs to be installed in advance mysqlclient rely on

#  rely on 
pip3 install mysqlclient
pip3 install Flask-SQLAlchemy

Flask-SQLAlchemy The configuration to connect to the database is as follows ：

app.config['SQLALCHEMY_DATABASE_URI'] = 'mysql:// user name : password @ Database address / Database to connect to '

SQLALCHEMY_DATABASE_URI, database URI Unified resource locator , Is a string used to identify the resource name

If you want to configure multiple databases , You can use it this way

SQLALCHEMY_BINDS = {
    'mysql': 'mysqldb://localhost/ database ',
    'sqlite': 'sqlite:////path/to/ database '
}

ORM Model creation

stay PyCharm Create a new Flask project flask-sqlalchemy

Use ORM The model needs to be bound to Flask object , stay app.py Created in Flask After object , Bind objects to the database

from flask_sqlalchemy import SQLAlchemy

#  Configure database connections 
app.config['SQLALCHEMY_DATABASE_URI'] = 'mysql://root:[email protected]/flask'
#  binding Flask object 
db = SQLAlchemy(app)

Then the database model is designed in this file User

#  Design database model 
class User(db.Model):
    #  Specify the table name 
    # __tablename__ = 'user'
    id = db.Column(db.Integer, primary_key=True)
    username = db.Column(db.String(64), nullable=False)
    password = db.Column(db.String(256), nullable=False)
    birth_date = db.Column(db.Date, nullable=True)
    age = db.Column(db.Integer, default=0)

Execute the create command input in the terminal python3 , Create a table or delete a table by executing the following command

from app import db
db.create_all() #  Create all tables 
db.drop_all() #  Delete all tables 

Exit the command line , Re enter , Delete first , Then execute the creation , When the table name is not specified, the default table name is sys+ The model name is lowercase

ORM Model field type

Field type	Field description
Integer/Float	Integer types / Floating point type
String(size)	character string , adopt max_lenght Specify string length
Text	Long text
DateTime	Time type , Corresponding datetime
Boolean	Boolean type
PickleType	Stored as a persistent Python object
LargeBinary	Store an arbitrarily large binary data