Tasks/backend/DATABASE_REFERENCE.md

Database Quick Reference

Database Connection Test

To test the database connection at any time:

npm run test:db

This will:

• Verify MySQL server is running
• Check database credentials
• Confirm database exists
• Show MySQL version
• List existing tables

Sequelize CLI Commands

Database Creation

Create the database manually:

mysql -u root -p -e "CREATE DATABASE interview_quiz_db CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;"

Migrations

Generate a new migration:

npx sequelize-cli migration:generate --name migration-name

Run all pending migrations:

npm run migrate

Undo last migration:

npm run migrate:undo

Check migration status:

npm run migrate:status

Seeders

Generate a new seeder:

npx sequelize-cli seed:generate --name seeder-name

Run all seeders:

npm run seed

Undo all seeders:

npm run seed:undo

Undo specific seeder:

npx sequelize-cli db:seed:undo --seed seeder-filename.js

Configuration Files

.sequelizerc

Configures Sequelize CLI paths for:

• config
• models-path
• seeders-path
• migrations-path

config/database.js

Contains environment-specific database configurations:

• development - Local development
• test - Testing environment
• production - Production settings

config/db.js

Database utility functions:

• testConnection() - Test database connection
• syncModels() - Sync models with database
• closeConnection() - Close database connection
• getDatabaseStats() - Get database statistics

models/index.js

• Initializes Sequelize
• Loads all model files
• Sets up model associations
• Exports db object with all models

Connection Pool Configuration

Current settings (from .env):

• DB_POOL_MAX=10 - Maximum connections
• DB_POOL_MIN=0 - Minimum connections
• DB_POOL_ACQUIRE=30000 - Max time to get connection (ms)
• DB_POOL_IDLE=10000 - Max idle time before release (ms)

Server Integration

The server (server.js) now:

1. Tests database connection on startup
2. Provides database stats in /health endpoint
3. Warns if database connection fails

Test the health endpoint:

curl http://localhost:3000/health

Response includes:

{
  "status": "OK",
  "message": "Interview Quiz API is running",
  "timestamp": "2025-11-09T...",
  "environment": "development",
  "database": {
    "connected": true,
    "version": "8.0.42",
    "tables": 0,
    "database": "interview_quiz_db"
  }
}

Troubleshooting

Connection Failed

If database connection fails, check:

1. MySQL server is running
2. Database credentials in .env are correct
3. Database exists
4. User has proper permissions

Access Denied

# Grant permissions to user
mysql -u root -p -e "GRANT ALL PRIVILEGES ON interview_quiz_db.* TO 'root'@'localhost';"
mysql -u root -p -e "FLUSH PRIVILEGES;"

Database Not Found

# Create database
mysql -u root -p -e "CREATE DATABASE interview_quiz_db CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;"

Check MySQL Service

Windows:

net start MySQL80

Linux/Mac:

sudo systemctl start mysql
# or
brew services start mysql

Next Steps

After Task 2 completion, you can:

1. ✅ Test database connection
2. 🔄 Start creating migrations (Task 4+)
3. 🔄 Build Sequelize models
4. 🔄 Run migrations to create tables
5. 🔄 Seed database with initial data

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Status: Database setup complete and verified! ✅