Sequelize V5.9.4 MVC模式（五 | 一对多）

大家可以前往 Sequelize中文文档，查看 Sequelize不同版本【5.x、4.x】的文档

本文档分多个篇章，难易程度从低到高，学习此篇章之前，务必确保自己已经掌握 node.js、express、es6语法、mysql等关系型数据库的sql语法等

一对多

以下例子可能不恰当，但是不要较真，跟着思路走就对了。
举个栗子： 假设一个人（id）可以有多个爱好（id），那么这种模式就是一对多

模型定义

我这里为了方便理解就不把hobbys表的模型拎出去了

import Sequelize from 'sequelize'
import sequelize from './../connection'

const User = sequelize.define('user', {
    username: Sequelize.STRING,
    gender: {
        type: Sequelize.INTEGER,
        defaultValue: 1,
    },
    age: {
        type: Sequelize.INTEGER,
        defaultValue: 20
    },
    headImg: {
        type: Sequelize.STRING,
        defaultValue: 'img.png'
    }
});
const Hobby = sequelize.define('hobby',
    {
        hobbyName: {
            type: Sequelize.CHAR(20),
            allowNull: false
        }
    }
);

//User的实例对象将拥有getHobby、setHobby、addHobby、createHobby、removeHobby、hasHobby方法
let Hobbies = User.hasMany(Hobby, {as: 'Hobbies'});//让user实例可以调用getHobbies 和 setHobbies
//Hobby的实例对象将拥有getUser、setUser、createUser方法
Hobby.belongsTo(User);

User.sync({force: true}).then(d=> {//表同步完成后注释掉
    console.log('users表同步完成');
    Hobby.sync({force: true}).then(d=> {
        console.log('Hobby表同步完成');
    });
});

export default {User,Hobby,Hobbies}

关系操作

增加数据

方法一

User.Controller.js

insertUserHobby: async (req, res, next) => {
        let {username, hobbyName} = req.body;
        let user = await User.User.create({username});
        let hobby = await user.createHobby({hobbyName});
        res.send({
            code: 200,
            hobby
        })
    },

方法二

User.Controller.js

insertUserHobbies: async (req, res, next) => {
        let {username, hobbyName} = req.body;
        let user = await User.User.create({username});
        let hobby1 = await User.Hobby.create({hobbyName});//插入一条hobby数据，此时该条数据的外键userId为空
        let hobby2 = await User.Hobby.create({hobbyName: '篮球'});//这里我就不接收了，直接赋值了
        hobby1 = await user.addHobby(hobby1);//使用user的属性id值再更新该条hobby数据，设置好外键，完成关系建立
        hobby2 = await user.addHobby(hobby2);//新增多个爱好
        res.send({
            code: 200,
            hobby1,hobby2
        })
    },

修改数据

User.Controller.js

updateUserHobbies: async (req, res, next)=>{
        let {id, hobbyName} = req.body;
        let user = await User.User.findOne({where: {id}});
        let upHobby = await User.Hobby.create({hobbyName});
        let upHobby2 = await User.Hobby.create({hobbyName: '爱好2'});
        let updateHobby = await user.setHobbies([upHobby, upHobby2]);
        res.send({
            code: 200,
            data: '修改成功',
            updateHobby
        })
    },

修改数据

删除数据 实际上是将关联的userId设置为null

User.Controller.js

deleteUserHobbies: async (req, res, next)=>{
        let {id} = req.body;
        let user = await User.User.findOne({where: {id}});//通过id查询用户
        let deleteHobby = await user.setHobbies([]);
        res.send({
            code: 200,
            data: '删除成功',
            deleteHobby
        })
    },

查询数据

查询user的所有满足条件的hobby数据。

User.Controller.js

getHobbies : async (req, res, next)=>{
        let {id} = req.query;
        let user = await User.User.findByPk(id);
        let Hobbies = await user.getHobbies({
            attributes: ['hobbyName','userId']
        });
        res.send({
            code: 200,
            hobbies
        })
    }

postman

{
    "code": 200,
    "hobbies": [
        {
            "hobbyName": "练习生",
            "userId": 4
        },
        {
            "hobbyName": "篮球",
            "userId": 4
        }
    ]
}

查询所有满足条件的hobby，同时获取hobby属于哪个user。

User.Controller.js

getUserHobbies: async (req, res, next)=>{
        let {id} = req.query;
        let hobbies = await User.Hobby.findAll({
            where: {userId: id},
            include: [{
                model: User.User,
                attributes: ['username']
            }],
            attributes: ['hobbyName','userId']
        });
        res.send({code: 200, hobbies})
    }

postman

{
    "code": 200,
    "hobbies": [
        {
            "hobbyName": "练习生",
            "userId": 4,
            "user": {
                "username": "Mjhu"
            }
        },
        {
            "hobbyName": "篮球",
            "userId": 4,
            "user": {
                "username": "Mjhu"
            }
        }
    ]
}

查询所有满足条件的user，同时获取该user所有满足条件的hobby。

User.Controller.js

getUserInfo: async (req, res, next)=>{
        let {id} = req.query;
        let userAndHobbies = await User.User.findOne({
            where: {id},
            attributes: ['username','gender'],
            include: [{
                association: User.Hobbies,
                attributes: ['hobbyName']
            }]
        });
        res.send({code: 200, userAndHobbies})
    }

postman

{
    "code": 200,
    "userAndHobbies": {
        "username": "Mjhu",
        "gender": 1,
        "Hobbies": [
            {
                "hobbyName": "练习生"
            },
            {
                "hobbyName": "篮球"
            }
        ]
    }
}

好了，到此为止，一对多的关系就已经结束了，下一章节我们会介绍 [Sequelize V5.9.4 中数据表的关系：多对多