Sequelize是Nodejs生态中一个比较出名的ORM框架。通过ORM框架，可以使用对象来操作数据库表数据，提高了开发效率和代码可读性，也方便后期维护。
今天主要介绍通过迁移[Migration]来创建数据库，表。
迁移的好处，可以类比git。通过每次创建迁移文件，来支持更新，回滚数据库表结构，也方便协同开发，也避免人工手动去直接修改数据库，用代码自动管理。换个电脑，也不用去拷贝数据库，直接运行迁移就可以完全恢复开发环境，极大减轻了心智负担。
1. 创建项目, 安装node package依赖
mkdir node_workcd node_workmkdir appnpm init -ynpm i sequelize-cli sequelize mysql2 koa2. 初始化Sequelize
npx sequelize init运行之后，会产生四个目录：
config, migrations, models, seeders
config:
{ "development": { "username": "root", "password": "root", "database": "app_development", "host": "127.0.0.1", "port": 8889, "dialect": "mysql", "timezone": "+08:00" }, "test": { "username": "root", "password": null, "database": "app_test", "host": "127.0.0.1", "dialect": "mysql" }, "production": { "username": "root", "password": null, "database": "app_production", "host": "127.0.0.1", "dialect": "mysql" }}环境env => {配置}
不同环境，对应不同的配置，也可以自定义环境，比如home
env指的是process.env.NODE_ENV，
可以通过设置环境变量来改变，比如export NODE_ENV=production；
迁移时候，也可以指定环境：npx sequelize db:migrate --env production，来连接production对应配置的数据库
创建数据库：
npx sequelize db:create说明npx是npm5.2之后，自带的一个命令。可以不用全局安装sequelize，使用时候，如果本地没有，就去npm仓库下载；下载完后或者本地已经下载过，就运行脚本命令。这样可以避免本地全局包过期，环境问题，每次都使用最新版本migrations: 迁移文件
npx sequelize model:generate --name User --attributes username:string执行后，会生成20180918055558-create-user.js迁移文件，和models/user.js模型文件
其他字段可以在迁移文件中补全，最后再运行npx sequelize db:migrate，就可以在数据库中看到生成了users表
'use strict'; module.exports = { up: (queryInterface, Sequelize) => { return queryInterface.createTable('Users', { id: { allowNull: false, autoIncrement: true, primaryKey: true, type: Sequelize.INTEGER }, username: { type: Sequelize.STRING(20), allowNull: false }, password: { type: Sequelize.CHAR(32), allowNull: false }, createdAt: { allowNull: false, type: Sequelize.DATE }, updatedAt: { allowNull: false, type: Sequelize.DATE } }, { tableName: 'users', charset: 'utf8mb4', collate: 'utf8mb4_bin', define: { timestamps: true } }).then(() => { // 添加索引 return queryInterface.addIndex('users', { name: 'username', unique: true, fields: ['username'] }); }); }, // 回退时执行，删除表 down: (queryInterface, Sequelize) => { return queryInterface.dropTable('Users'); } };执行迁移：
npx sequelize db:migratenpx sequelize db:migrate:all撤销迁移：
npx sequelize db:migrate:undo 最近一次的npx sequelize db:migrate:undo:allnpx sequelize db:migrate:undo:all --to XXXXXXXXXXXXXX-create-posts.js--from, --to 参数，可以指定迁移文件
models: 模型文件
model:generate生成的model都在这个目录中
'use strict';module.exports = { up: (queryInterface, Sequelize) => { return queryInterface.createTable('Users', { id: { allowNull: false, autoIncrement: true, primaryKey: true, type: Sequelize.INTEGER }, username: { type: Sequelize.STRING(20), allowNull: false }, password: { type: Sequelize.CHAR(32), allowNull: false }, createdAt: { allowNull: false, type: Sequelize.DATE }, updatedAt: { allowNull: false, type: Sequelize.DATE } }, { tableName: 'users', charset: 'utf8mb4', collate: 'utf8mb4_bin', }).then(() => { return queryInterface.addIndex('users', { name: 'username', unique: true, fields: ['username'] }); }); }, down: (queryInterface, Sequelize) => { return queryInterface.dropTable('Users'); }};模型对象创建，默认会自动赋值，更新createdAt, updatedAt两个timestamps字段。下边会给出完整示例。
seeders: 填充数据文件
创建seed文件：
npx sequelize seed:generate --name demo-user执行之后，会得到20180918090545-demo-user.js
'use strict';const md5 = require('md5')module.exports = { up: (queryInterface, Sequelize) => { return queryInterface.bulkInsert('Users', [ { username: 'Kimoo', password: md5('123456'), createdAt: new Date(), updatedAt: new Date(), }, { username: 'Reci', password: md5('123321'), createdAt: new Date(), updatedAt: new Date(), } ], {}); }, down: (queryInterface, Sequelize) => { /* Add reverting commands here. Return a promise to correctly handle asynchronicity. Example: return queryInterface.bulkDelete('Person', null, {}); */ return queryInterface.bulkDelete('Users', null, {}); }};填充数据：
npx sequelize db:seed:all撤销数据：
npx sequelize db:seed:undo 最近一次的npx sequelize db:seed:undo --seed name-of-seed-as-in-data 具体某个npx sequelize db:seed:undo:all3. 具体实践
app.js
(async function() { const Koa = require('koa'); const KoaStaticCache = require('koa-static-cache'); const KoaBodyParser = require('koa-bodyparser'); const router = require('./routers/main'); const Session = require('koa-session'); const app = new Koa(); // app.keys = new KeyGrip(['im a newer secret', 'i like turtle'], 'sha256'); app.keys = ['app']; app.use( Session({ key: 'koa:sess', maxAge: 86400000, autoCommit: true, overwrite: true, httpOnly: true, signed: true, rolling: false, renew: false }, app) ); // app.use( async (ctx, next) => { // ctx.set('Access-Control-Allow-Origin','*'); // await next(); // } ); app.use( KoaStaticCache('./public', { prefix: 'public', gzip: true }) ); app.use( KoaBodyParser() ); app.use( router.routes() ); app.listen(8088);})();models/index.js
'use strict';const fs = require('fs');const path = require('path');const Sequelize = require('sequelize');const basename = path.basename(__filename);const env = process.env.NODE_ENV || 'development';const config = require(__dirname + '/../config/config.json')[env];const db = {};let sequelize;if (config.use_env_variable) { sequelize = new Sequelize(process.env[config.use_env_variable], config);} else { sequelize = new Sequelize(config.database, config.username, config.password, config);}// 自动导入 models 文件夹下的所有文件，比如user.js这个模型文件// 自动加载模型并执行// let users = require('./users');// let UsersModel = users(sequelize, Sequelize);// db[UsersModel.name] = UsersModel; // db['Users'] = UsersModel;// 下面通过fs自动加载所有的文件，并执行，同时生成的模型对象挂载到db对象下面，最后返回出去fs .readdirSync(__dirname) .filter(file => { return (file.indexOf('.') !== 0) && (file !== basename) && (file.slice(-3) === '.js'); }) .forEach(file => { const model = sequelize['import'](path.join(__dirname, file)); db[model.name] = model; });Object.keys(db).forEach(modelName => { if (db[modelName].associate) { db[modelName].associate(db); }});db.sequelize = sequelize;db.Sequelize = Sequelize;module.exports = db;routers/main.js
const KoaRouter = require('koa-router');const md5 = require('md5');const Models = require('../models');const Sequelize = require('sequelize');const router = new KoaRouter();router.post('/register', async ctx => { // console.log(ctx.request.body); let username = ctx.request.body.username.trim(); let password = ctx.request.body.password.trim(); let repassword = ctx.request.body.repassword.trim(); if (username=='' || password == '' || repassword == '') { return ctx.body = { code: 1, data: '用户名或密码不能为空' } } if (password != repassword) { return ctx.body = { code: 2, data: '两次输入的密码不一致' } } let user = await Models.Users.findOne({ where: { username } }); if (user !== null) { return ctx.body = { code: 3, data: '当前用户已经被注册了' } } let newUser = await Models.Users.build({ username, password: md5(password) }).save(); ctx.body = { code: 0, data: { id: newUser.get('id'), username: newUser.get('username') } } }); router.post('/login', async ctx => { let username = ctx.request.body.username; let password = ctx.request.body.password; let user = await Models.Users.findOne({ where: { username } }); if (user === null) { return ctx.body = { code: 1, data: '不存在该用户' } } if (user.get('password') !== md5(password)) { return ctx.body = { code: 1, data: '密码错误' } } // ctx.cookies.set('uid', user.get('id'), { // httpOnly: false // }); // 服务端发送一个约定好的cookie，来表示当前是登录 // ctx.cookies.set('uid', user.get('id'), { // // httpOnly，表示当前的cookie是否允许客户端进行操作（js），如果为true，那么就表示这个cookie是能用户http协议的数据传输 // httpOnly: true, // signed: true // }); ctx.cookies.set('username', user.get('username'), { httpOnly: false }); ctx.session.uid = 1; ctx.body = { code: 0, data: { id: user.get('id'), username: user.get('username') } } });})module.exports = router;4. 测试接口，注册用户，添加数据
可以在postman中测试接口，地址http://localhost:8088/register，注册用户
node app.js