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DATABASE_REFERENCE.md

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+# Database Quick Reference
+
+## Database Connection Test
+
+To test the database connection at any time:
+
+```bash
+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:
+```bash
+mysql -u root -p -e "CREATE DATABASE interview_quiz_db CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;"
+```
+
+### Migrations
+
+Generate a new migration:
+```bash
+npx sequelize-cli migration:generate --name migration-name
+```
+
+Run all pending migrations:
+```bash
+npm run migrate
+```
+
+Undo last migration:
+```bash
+npm run migrate:undo
+```
+
+Check migration status:
+```bash
+npm run migrate:status
+```
+
+### Seeders
+
+Generate a new seeder:
+```bash
+npx sequelize-cli seed:generate --name seeder-name
+```
+
+Run all seeders:
+```bash
+npm run seed
+```
+
+Undo all seeders:
+```bash
+npm run seed:undo
+```
+
+Undo specific seeder:
+```bash
+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:
+```bash
+curl http://localhost:3000/health
+```
+
+Response includes:
+```json
+{
+  "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
+
+```bash
+# 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
+
+```bash
+# Create database
+mysql -u root -p -e "CREATE DATABASE interview_quiz_db CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;"
+```
+
+### Check MySQL Service
+
+Windows:
+```bash
+net start MySQL80
+```
+
+Linux/Mac:
+```bash
+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
+
+---
+
+**Status**: Database setup complete and verified! ✅