Flask one to many database creation, basic addition, deletion, modification and query

Common types of database fields

data type	explain
Integer	An integer (*****)
String (size)	String with length limit (*****)
Text	Some longer unicode Text (*****)
DateTime	Expressed as Python datetime Object's Time and date (*****)
Float	Store floating point values
Boolean	Store Boolean values
DECIMAL	Decimal system , Mostly used for price

One to many model class creation

from flask_sqlalchemy import SQLAlchemy

db = SQLAlchemy()

# 1. The establishment of a one to many relationship :  One party establishes a relationship ,  Establish foreign keys by multiple parties 

#  Professional model 
class Sub(db.Model):

    id = db.Column(db.Integer, primary_key=True)
    name = db.Column(db.String(32))
    #  One party defines the relationship ,  relation Stu Model , Stu Is the model class name ,
    # backref The value of is to " In many ways " Used to query " a party " Of 
    stu = db.relationship('Stu', backref='sub')  

#  Student model 
class Stu(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    name = db.Column(db.String(32))
    #  Multi party definition of foreign keys ,  relation sub.id 
    # sub It is the table name in the database, not the model class name 
    sub_id = db.Column(db.Integer, db.ForeignKey('sub.id'))

Flask-RESTful Provide RequestParser class , Used to help us verify and transform request data . It is designed to provide simple and unified access Flask.request The entry of any variable in the object

RequestParser() Optional fields for verification parameters （ part ）

Optional parameters	effect	Case study
type	Parameter type	type=int
help	Error message	help=“id Do not be empty ”
required	Whether must （ The default is Flase）	required=True
choices	A specific value	choices=[‘ male ’,‘ Woman ’]
default	If you don't pass , The default value is	default=18

Additions and deletions

Inquire about

from flask import Blueprint, jsonify
from models.model import *
from flask_restful import marshal, fields, reqparse

    def get(self):
    	#  Get all the data of one party 
        sub = Sub.query.all()

		#  Serialized data 
		# marshal() Method to serialize data directly 
       	# sub:  Data to serialize 
        # {id...}:  Fields to serialize 
        data = marshal(sub, {
    
            "id": fields.Integer,
            "name": fields.String,
        })
        #  return json Format response 
        return jsonify({
    'code': 200, 'msg': ' Data acquisition success ', 'data': data})

increase

    def post(self):
    	#  structure RequestParser() object 
    	#  Instantiation 
        req = reqparse.RequestParser()
        #  Add verification field 
        req.add_argument("name")
        #  Optional parameters （ part ）
        # type=int #  Parameter type  
        # help="id Do not be empty " #  Error message 
        # required=True #  Whether must 
        # action="append" #  How to deal with parameters with the same name ,append Additional ,store  Keep the first 
        # choices=[' male ',' Woman '] #  A specific value 
        # default=18 #  If you don't pass , The default value is 
     
		#  Start inspection processing 
        args = req.parse_args()
        # 
        s1 = Sub(
            name=args["name"],
        )
        db.session.add(s1)
        #  Commit transaction 
        db.session.commit()

        return jsonify({
    'code': 200, 'msg': ' Data added successfully '})

modify

    def put(self):
        req = reqparse.RequestParser()
        req.add_argument("id")

        args = req.parse_args()
		#  The first method 
		#  Directly modifying 
        Sub.query.filter(Sub.id == args["id"]).update(
            args
        )
        #  The second method 
        #  First get   Then assign value and modify 
        sub = Sub.query.filter(Sub.id == args["id"]).first()
        #  assignment 
        sub.name=args["name"]
        #  Commit transaction 
        db.session.commit()
        
        return jsonify({
    'code': 200, 'msg': ' Data modified successfully '})  
        

Delete

    def delete(self):
        req = reqparse.RequestParser()
        req.add_argument("id")
        args = req.parse_args()

        Sub.query.filter(Sub.id == args['id']).delete()

        db.session.commit()

        return jsonify({
    'code': 200, 'msg': ' Data deletion successful '})