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SEQUELIZE_QUICK_REFERENCE.md
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SEQUELIZE_QUICK_REFERENCE.md
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# Sequelize Quick Reference Guide
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## Common Operations for Interview Quiz App
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### 1. Database Connection
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```javascript
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// config/database.js
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const { Sequelize } = require('sequelize');
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const sequelize = new Sequelize(
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process.env.DB_NAME,
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process.env.DB_USER,
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process.env.DB_PASSWORD,
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{
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host: process.env.DB_HOST,
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dialect: 'mysql',
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pool: { max: 10, min: 0, acquire: 30000, idle: 10000 }
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}
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);
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// Test connection
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sequelize.authenticate()
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.then(() => console.log('MySQL connected'))
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.catch(err => console.error('Unable to connect:', err));
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module.exports = sequelize;
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```
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---
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### 2. User Operations
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#### Register New User
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```javascript
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const bcrypt = require('bcrypt');
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const { User } = require('../models');
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const registerUser = async (userData) => {
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const hashedPassword = await bcrypt.hash(userData.password, 10);
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const user = await User.create({
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username: userData.username,
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email: userData.email,
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password: hashedPassword,
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role: 'user'
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});
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return user;
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};
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```
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#### Login User
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```javascript
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const loginUser = async (email, password) => {
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const user = await User.findOne({
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where: { email },
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attributes: ['id', 'username', 'email', 'password', 'role']
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});
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if (!user) {
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throw new Error('User not found');
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}
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const isValid = await bcrypt.compare(password, user.password);
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if (!isValid) {
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throw new Error('Invalid credentials');
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}
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return user;
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};
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```
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#### Get User Dashboard
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```javascript
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const getUserDashboard = async (userId) => {
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const user = await User.findByPk(userId, {
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attributes: [
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'id', 'username', 'email',
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'totalQuizzes', 'totalQuestions', 'correctAnswers', 'streak'
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],
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include: [
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{
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model: QuizSession,
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where: { status: 'completed' },
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required: false,
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limit: 10,
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order: [['completedAt', 'DESC']],
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include: [{ model: Category, attributes: ['name'] }]
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}
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]
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});
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return user;
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};
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```
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---
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### 3. Category Operations
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#### Get All Categories
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```javascript
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const getCategories = async () => {
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const categories = await Category.findAll({
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where: { isActive: true },
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attributes: {
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include: [
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[
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sequelize.literal(`(
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SELECT COUNT(*)
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FROM questions
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WHERE questions.category_id = categories.id
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AND questions.is_active = true
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)`),
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'questionCount'
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]
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]
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}
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});
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return categories;
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};
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```
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#### Get Guest-Accessible Categories
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```javascript
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const getGuestCategories = async () => {
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const categories = await Category.findAll({
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where: {
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isActive: true,
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guestAccessible: true
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},
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attributes: ['id', 'name', 'description', 'icon', 'publicQuestionCount']
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});
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return categories;
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};
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```
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---
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### 4. Question Operations
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#### Create Question (Admin)
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```javascript
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const createQuestion = async (questionData) => {
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const question = await Question.create({
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question: questionData.question,
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type: questionData.type,
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categoryId: questionData.categoryId,
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difficulty: questionData.difficulty,
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options: JSON.stringify(questionData.options), // Store as JSON
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correctAnswer: questionData.correctAnswer,
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explanation: questionData.explanation,
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keywords: JSON.stringify(questionData.keywords),
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tags: JSON.stringify(questionData.tags),
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visibility: questionData.visibility || 'registered',
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isGuestAccessible: questionData.isGuestAccessible || false,
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createdBy: questionData.userId
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});
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// Update category question count
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await Category.increment('questionCount', {
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where: { id: questionData.categoryId }
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});
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return question;
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};
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```
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#### Get Questions by Category
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```javascript
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const getQuestionsByCategory = async (categoryId, options = {}) => {
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const { difficulty, limit = 10, visibility = 'registered' } = options;
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const where = {
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categoryId,
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isActive: true,
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visibility: {
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[Op.in]: visibility === 'guest' ? ['public'] : ['public', 'registered', 'premium']
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}
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};
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if (difficulty) {
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where.difficulty = difficulty;
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}
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const questions = await Question.findAll({
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where,
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order: sequelize.random(),
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limit,
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include: [{ model: Category, attributes: ['name'] }]
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});
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return questions;
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};
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```
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#### Search Questions (Full-Text)
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```javascript
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const searchQuestions = async (searchTerm) => {
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const questions = await Question.findAll({
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where: {
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[Op.or]: [
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sequelize.literal(`MATCH(question, explanation) AGAINST('${searchTerm}' IN NATURAL LANGUAGE MODE)`)
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],
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isActive: true
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},
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limit: 50
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});
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return questions;
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};
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```
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---
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### 5. Quiz Session Operations
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#### Start Quiz Session
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```javascript
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const startQuizSession = async (sessionData) => {
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const { userId, guestSessionId, categoryId, questionCount, difficulty } = sessionData;
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// Create quiz session
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const quizSession = await QuizSession.create({
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userId: userId || null,
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guestSessionId: guestSessionId || null,
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isGuestSession: !userId,
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categoryId,
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totalQuestions: questionCount,
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status: 'in-progress',
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startTime: new Date()
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});
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// Get random questions
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const questions = await Question.findAll({
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where: {
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categoryId,
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difficulty: difficulty || { [Op.in]: ['easy', 'medium', 'hard'] },
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isActive: true
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},
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order: sequelize.random(),
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limit: questionCount
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});
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// Create junction entries
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const sessionQuestions = questions.map((q, index) => ({
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quizSessionId: quizSession.id,
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questionId: q.id,
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questionOrder: index + 1
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}));
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await sequelize.models.QuizSessionQuestion.bulkCreate(sessionQuestions);
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return { quizSession, questions };
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};
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```
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#### Submit Answer
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```javascript
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const submitAnswer = async (answerData) => {
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const { quizSessionId, questionId, userAnswer } = answerData;
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// Get question
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const question = await Question.findByPk(questionId);
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// Check if correct
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const isCorrect = question.correctAnswer === userAnswer;
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// Save answer
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const answer = await QuizAnswer.create({
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quizSessionId,
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questionId,
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userAnswer,
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isCorrect,
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timeSpent: answerData.timeSpent || 0
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});
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// Update quiz session score
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if (isCorrect) {
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await QuizSession.increment('score', { where: { id: quizSessionId } });
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}
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// Update question statistics
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await Question.increment('timesAttempted', { where: { id: questionId } });
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return {
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isCorrect,
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correctAnswer: question.correctAnswer,
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explanation: question.explanation
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};
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};
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```
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#### Complete Quiz Session
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```javascript
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const completeQuizSession = async (sessionId) => {
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const session = await QuizSession.findByPk(sessionId, {
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include: [
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{
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model: QuizAnswer,
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include: [{ model: Question, attributes: ['id', 'question'] }]
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}
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]
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});
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// Calculate results
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const correctAnswers = session.QuizAnswers.filter(a => a.isCorrect).length;
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const percentage = (correctAnswers / session.totalQuestions) * 100;
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const timeTaken = Math.floor((new Date() - session.startTime) / 1000); // seconds
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// Update session
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await session.update({
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status: 'completed',
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endTime: new Date(),
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completedAt: new Date()
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});
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// Update user stats if not guest
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if (session.userId) {
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await User.increment({
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totalQuizzes: 1,
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totalQuestions: session.totalQuestions,
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correctAnswers: correctAnswers
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}, { where: { id: session.userId } });
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}
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return {
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score: session.score,
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totalQuestions: session.totalQuestions,
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percentage,
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timeTaken,
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correctAnswers,
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incorrectAnswers: session.totalQuestions - correctAnswers,
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results: session.QuizAnswers
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};
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};
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```
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---
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### 6. Guest Session Operations
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#### Create Guest Session
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```javascript
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const createGuestSession = async (deviceId, ipAddress, userAgent) => {
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const guestId = `guest_${Date.now()}_${Math.random().toString(36).substr(2, 9)}`;
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const sessionToken = jwt.sign({ guestId }, process.env.JWT_SECRET, { expiresIn: '24h' });
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const expiresAt = new Date(Date.now() + 24 * 60 * 60 * 1000); // 24 hours
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const guestSession = await GuestSession.create({
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guestId,
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deviceId,
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sessionToken,
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quizzesAttempted: 0,
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maxQuizzes: 3,
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expiresAt,
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ipAddress,
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userAgent
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});
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return guestSession;
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};
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```
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#### Check Guest Quiz Limit
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```javascript
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const checkGuestQuizLimit = async (guestSessionId) => {
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const session = await GuestSession.findByPk(guestSessionId);
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if (!session) {
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throw new Error('Guest session not found');
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}
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if (new Date() > session.expiresAt) {
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throw new Error('Guest session expired');
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}
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const remainingQuizzes = session.maxQuizzes - session.quizzesAttempted;
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if (remainingQuizzes <= 0) {
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throw new Error('Guest quiz limit reached');
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}
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return {
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remainingQuizzes,
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resetTime: session.expiresAt
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};
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};
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```
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---
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### 7. Bookmark Operations
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#### Add Bookmark
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```javascript
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const addBookmark = async (userId, questionId) => {
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const bookmark = await sequelize.models.UserBookmark.create({
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userId,
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questionId
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});
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return bookmark;
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};
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```
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#### Get User Bookmarks
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```javascript
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const getUserBookmarks = async (userId) => {
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const user = await User.findByPk(userId, {
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include: [{
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model: Question,
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as: 'bookmarks',
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through: { attributes: ['bookmarkedAt'] },
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include: [{ model: Category, attributes: ['name'] }]
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}]
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});
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return user.bookmarks;
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};
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```
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#### Remove Bookmark
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```javascript
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const removeBookmark = async (userId, questionId) => {
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await sequelize.models.UserBookmark.destroy({
|
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where: { userId, questionId }
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});
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||||
};
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```
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||||
---
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### 8. Admin Operations
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#### Get System Statistics
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```javascript
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const getSystemStats = async () => {
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const [totalUsers, activeUsers, totalQuizzes] = await Promise.all([
|
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User.count(),
|
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User.count({
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where: {
|
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lastLogin: { [Op.gte]: new Date(Date.now() - 7 * 24 * 60 * 60 * 1000) }
|
||||
}
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||||
}),
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QuizSession.count({ where: { status: 'completed' } })
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]);
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const popularCategories = await Category.findAll({
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attributes: [
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'id', 'name',
|
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[sequelize.fn('COUNT', sequelize.col('QuizSessions.id')), 'quizCount']
|
||||
],
|
||||
include: [{
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||||
model: QuizSession,
|
||||
attributes: [],
|
||||
required: false
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||||
}],
|
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group: ['Category.id'],
|
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order: [[sequelize.literal('quizCount'), 'DESC']],
|
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limit: 5
|
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});
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||||
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||||
const avgScore = await QuizSession.findOne({
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attributes: [[sequelize.fn('AVG', sequelize.col('score')), 'avgScore']],
|
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where: { status: 'completed' }
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||||
});
|
||||
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return {
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totalUsers,
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activeUsers,
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totalQuizzes,
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popularCategories,
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||||
averageScore: avgScore.dataValues.avgScore || 0
|
||||
};
|
||||
};
|
||||
```
|
||||
|
||||
#### Update Guest Settings
|
||||
```javascript
|
||||
const updateGuestSettings = async (settings, adminUserId) => {
|
||||
const guestSettings = await GuestSettings.findOne();
|
||||
|
||||
if (guestSettings) {
|
||||
await guestSettings.update({
|
||||
...settings,
|
||||
updatedBy: adminUserId
|
||||
});
|
||||
} else {
|
||||
await GuestSettings.create({
|
||||
...settings,
|
||||
updatedBy: adminUserId
|
||||
});
|
||||
}
|
||||
|
||||
return guestSettings;
|
||||
};
|
||||
```
|
||||
|
||||
---
|
||||
|
||||
### 9. Transaction Example
|
||||
|
||||
```javascript
|
||||
const { Op } = require('sequelize');
|
||||
|
||||
const convertGuestToUser = async (guestSessionId, userData) => {
|
||||
const t = await sequelize.transaction();
|
||||
|
||||
try {
|
||||
// Create user
|
||||
const user = await User.create(userData, { transaction: t });
|
||||
|
||||
// Get guest session
|
||||
const guestSession = await GuestSession.findByPk(guestSessionId, { transaction: t });
|
||||
|
||||
// Migrate quiz sessions
|
||||
await QuizSession.update(
|
||||
{ userId: user.id, isGuestSession: false },
|
||||
{ where: { guestSessionId }, transaction: t }
|
||||
);
|
||||
|
||||
// Calculate stats
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||||
const stats = await QuizSession.findAll({
|
||||
where: { userId: user.id },
|
||||
attributes: [
|
||||
[sequelize.fn('COUNT', sequelize.col('id')), 'totalQuizzes'],
|
||||
[sequelize.fn('SUM', sequelize.col('score')), 'totalScore']
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||||
],
|
||||
transaction: t
|
||||
});
|
||||
|
||||
// Update user stats
|
||||
await user.update({
|
||||
totalQuizzes: stats[0].dataValues.totalQuizzes || 0
|
||||
}, { transaction: t });
|
||||
|
||||
// Delete guest session
|
||||
await guestSession.destroy({ transaction: t });
|
||||
|
||||
await t.commit();
|
||||
return user;
|
||||
} catch (error) {
|
||||
await t.rollback();
|
||||
throw error;
|
||||
}
|
||||
};
|
||||
```
|
||||
|
||||
---
|
||||
|
||||
### 10. Common Query Operators
|
||||
|
||||
```javascript
|
||||
const { Op } = require('sequelize');
|
||||
|
||||
// Examples of common operators
|
||||
const examples = {
|
||||
// Equals
|
||||
{ status: 'completed' },
|
||||
|
||||
// Not equals
|
||||
{ status: { [Op.ne]: 'abandoned' } },
|
||||
|
||||
// Greater than / Less than
|
||||
{ score: { [Op.gte]: 80 } },
|
||||
{ createdAt: { [Op.lte]: new Date() } },
|
||||
|
||||
// Between
|
||||
{ score: { [Op.between]: [50, 100] } },
|
||||
|
||||
// In array
|
||||
{ difficulty: { [Op.in]: ['easy', 'medium'] } },
|
||||
|
||||
// Like (case-sensitive)
|
||||
{ question: { [Op.like]: '%javascript%' } },
|
||||
|
||||
// Not null
|
||||
{ userId: { [Op.not]: null } },
|
||||
|
||||
// OR condition
|
||||
{
|
||||
[Op.or]: [
|
||||
{ visibility: 'public' },
|
||||
{ isGuestAccessible: true }
|
||||
]
|
||||
},
|
||||
|
||||
// AND condition
|
||||
{
|
||||
[Op.and]: [
|
||||
{ isActive: true },
|
||||
{ difficulty: 'hard' }
|
||||
]
|
||||
}
|
||||
};
|
||||
```
|
||||
|
||||
---
|
||||
|
||||
## Error Handling
|
||||
|
||||
```javascript
|
||||
const handleSequelizeError = (error) => {
|
||||
if (error.name === 'SequelizeUniqueConstraintError') {
|
||||
return { status: 400, message: 'Record already exists' };
|
||||
}
|
||||
|
||||
if (error.name === 'SequelizeValidationError') {
|
||||
return { status: 400, message: error.errors.map(e => e.message).join(', ') };
|
||||
}
|
||||
|
||||
if (error.name === 'SequelizeForeignKeyConstraintError') {
|
||||
return { status: 400, message: 'Invalid foreign key reference' };
|
||||
}
|
||||
|
||||
return { status: 500, message: 'Database error' };
|
||||
};
|
||||
```
|
||||
|
||||
---
|
||||
|
||||
## Best Practices
|
||||
|
||||
1. **Always use parameterized queries** (Sequelize does this by default)
|
||||
2. **Use transactions for multi-step operations**
|
||||
3. **Index frequently queried columns**
|
||||
4. **Use eager loading to avoid N+1 queries**
|
||||
5. **Limit result sets with pagination**
|
||||
6. **Use connection pooling**
|
||||
7. **Handle errors gracefully**
|
||||
8. **Log slow queries in development**
|
||||
9. **Use prepared statements**
|
||||
10. **Validate input before database operations**
|
||||
|
||||
---
|
||||
|
||||
Happy coding! 🚀
|
||||
Reference in New Issue
Block a user