العلاقات والاستعلامات في ORM

const express = require('express');const { Author, Book, seed } = require('./models'); const app = express(); app.get('/api/books', async (req, res) => {  const books = await Book.findAll({    include: { model: Author, attributes: ['name'] },    order: [['year', 'DESC']],  });  res.json(books);}); app.get('/api/authors/:id', async (req, res) => {  const author = await Author.findByPk(req.params.id, { include: Book });  if (!author) return res.status(404).json({ error: 'غير موجود' });  res.json(author);}); seed().then(() => app.listen(3000));

// models.js: النماذج والعلاقات في مكان واحدconst { Sequelize, DataTypes } = require('sequelize');const sequelize = new Sequelize({ dialect: 'sqlite', storage: ':memory:', logging: false }); const Author = sequelize.define('Author', {  name: { type: DataTypes.STRING, allowNull: false },}, { timestamps: false }); const Book = sequelize.define('Book', {  title: { type: DataTypes.STRING, allowNull: false },  year: DataTypes.INTEGER,}, { timestamps: false }); // واحد إلى متعدد: المؤلف له كتب كثيرة، والكتاب لمؤلف واحدAuthor.hasMany(Book);        // يضيف العمود AuthorId إلى جدول BooksBook.belongsTo(Author); async function seed() {  await sequelize.sync();  const sara = await Author.create({ name: 'سارة' });  const khaled = await Author.create({ name: 'خالد' });  await Book.bulkCreate([    { title: 'تعلم JavaScript', year: 2021, AuthorId: sara.id },    { title: 'React خطوة بخطوة', year: 2024, AuthorId: sara.id },    { title: 'أساسيات الويب', year: 2023, AuthorId: khaled.id },  ]);} module.exports = { sequelize, Author, Book, seed };

const express = require('express');const { sequelize, Author, Book, seed } = require('./models');const app = express(); app.get('/slow', async (req, res) => {  const books = await Book.findAll();  const out = [];  for (const b of books) {    const a = await b.getAuthor();            // استعلام لكل كتاب!    out.push({ title: b.title, author: a.name });  }  res.json(out);}); app.get('/fast', async (req, res) => {  const books = await Book.findAll({ include: Author });   // استعلام واحد  res.json(books.map(b => ({ title: b.title, author: b.Author.name })));}); seed().then(() => {  sequelize.options.logging = (sql) =>    console.log('استعلام:', sql.slice(21, 60) + (sql.includes('JOIN') ? ' … LEFT OUTER JOIN …' : ' …'));  app.listen(3000);});

// models.js: النماذج والعلاقات في مكان واحدconst { Sequelize, DataTypes } = require('sequelize');const sequelize = new Sequelize({ dialect: 'sqlite', storage: ':memory:', logging: false }); const Author = sequelize.define('Author', {  name: { type: DataTypes.STRING, allowNull: false },}, { timestamps: false }); const Book = sequelize.define('Book', {  title: { type: DataTypes.STRING, allowNull: false },  year: DataTypes.INTEGER,}, { timestamps: false }); // واحد إلى متعدد: المؤلف له كتب كثيرة، والكتاب لمؤلف واحدAuthor.hasMany(Book);        // يضيف العمود AuthorId إلى جدول BooksBook.belongsTo(Author); async function seed() {  await sequelize.sync();  const sara = await Author.create({ name: 'سارة' });  const khaled = await Author.create({ name: 'خالد' });  await Book.bulkCreate([    { title: 'تعلم JavaScript', year: 2021, AuthorId: sara.id },    { title: 'React خطوة بخطوة', year: 2024, AuthorId: sara.id },    { title: 'أساسيات الويب', year: 2023, AuthorId: khaled.id },  ]);} module.exports = { sequelize, Author, Book, seed };

const express = require('express');const { Sequelize, DataTypes } = require('sequelize');const sequelize = new Sequelize({ dialect: 'sqlite', storage: ':memory:', logging: false }); const Student = sequelize.define('Student', { name: DataTypes.STRING }, { timestamps: false });const Course = sequelize.define('Course', { code: DataTypes.STRING }, { timestamps: false });const Enrollment = sequelize.define('Enrollment', { grade: DataTypes.INTEGER }, { timestamps: false }); Student.belongsToMany(Course, { through: Enrollment });Course.belongsToMany(Student, { through: Enrollment }); const app = express();app.use(express.json()); app.post('/api/students/:id/courses', async (req, res) => {  const s = await Student.findByPk(req.params.id);  const c = await Course.findOne({ where: { code: req.body.code } });  if (!s || !c) return res.status(404).json({ error: 'غير موجود' });  await s.addCourse(c, { through: { grade: req.body.grade } });  res.status(201).json({ ok: true });}); app.get('/api/students/:id', async (req, res) => {  const s = await Student.findByPk(req.params.id, {    include: { model: Course, attributes: ['code'], through: { attributes: ['grade'] } },  });  res.json(s);}); sequelize.sync().then(async () => {  await Student.create({ name: 'ريم' });  await Course.bulkCreate([{ code: 'CS242' }, { code: 'CS241' }]);  app.listen(3000);});

const express = require('express');const { Sequelize, DataTypes } = require('sequelize');const sequelize = new Sequelize({ dialect: 'sqlite', storage: ':memory:', logging: false });const Account = sequelize.define('Account', { owner: DataTypes.STRING, balance: DataTypes.INTEGER }, { timestamps: false }); const app = express();app.use(express.json()); app.post('/api/transfer', async (req, res) => {  const { from, to, amount } = req.body;  try {    await sequelize.transaction(async (t) => {      const a = await Account.findByPk(from, { transaction: t });      const b = await Account.findByPk(to, { transaction: t });      await a.decrement('balance', { by: amount, transaction: t });      if (a.balance - amount < 0) throw new Error('الرصيد لا يكفي');      await b.increment('balance', { by: amount, transaction: t });    });    res.json({ ok: true });  } catch (err) {    res.status(400).json({ error: err.message });  }}); app.get('/api/accounts', async (req, res) => res.json(await Account.findAll())); sequelize.sync().then(async () => {  await Account.bulkCreate([{ owner: 'سارة', balance: 500 }, { owner: 'فهد', balance: 100 }]);  app.listen(3000);});