Chapter 5: Database Operations

5.1 Django Database Configuration

Supported Databases

Django officially supports multiple database backends:

• PostgreSQL - via django.db.backends.postgresql
• MySQL - via django.db.backends.mysql
• SQLite - via django.db.backends.sqlite3
• Oracle - via django.db.backends.oracle

Database Connection Configuration

Configure databases in settings.py:

# SQLite configuration example
DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.sqlite3',
        'NAME': BASE_DIR / 'db.sqlite3',
    }
}

# PostgreSQL configuration example
DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.postgresql',
        'NAME': 'mydatabase',
        'USER': 'mydatabaseuser',
        'PASSWORD': 'mypassword',
        'HOST': '127.0.0.1',
        'PORT': '5432',
    }
}

# MySQL configuration example
DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.mysql',
        'NAME': 'mydatabase',
        'USER': 'mydatabaseuser',
        'PASSWORD': 'mypassword',
        'HOST': '127.0.0.1',
        'PORT': '3306',
        'OPTIONS': {
            'charset': 'utf8mb4',
            'init_command': "SET sql_mode='STRICT_TRANS_TABLES'",
        },
    }
}

Configuration Parameter Explanation

• ENGINE: Database backend engine
• NAME: Database name (file path for SQLite)
• USER: Database username
• PASSWORD: Database password
• HOST: Database host address
• PORT: Database port
• OPTIONS: Additional database options

Multiple Database Configuration

Django supports configuring multiple database connections:

DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.postgresql',
        'NAME': 'primary_db',
        # ... other configurations
    },
    'read_replica': {
        'ENGINE': 'django.db.backends.postgresql',
        'NAME': 'replica_db',
        # ... other configurations
    },
    'analytics': {
        'ENGINE': 'django.db.backends.mysql',
        'NAME': 'analytics_db',
        # ... other configurations
    }
}

Database Routing

For multiple database configurations, database routing can be used to control data read/write:

# Configure database routing in settings.py
DATABASE_ROUTERS = ['path.to.PrimaryReplicaRouter']

# Database routing example
class PrimaryReplicaRouter:
    def db_for_read(self, model, **hints):
        return 'read_replica'

    def db_for_write(self, model, **hints):
        return 'default'

    def allow_relation(self, obj1, obj2, **hints):
        return True

    def allow_migrate(self, db, app_label, model_name=None, **hints):
        return db == 'default'

Environment Variable Configuration

In production environments, it's recommended to use environment variables to configure databases:

import os
from pathlib import Path

# Get configuration from environment variables
DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.postgresql',
        'NAME': os.getenv('DB_NAME', 'mydatabase'),
        'USER': os.getenv('DB_USER', 'myuser'),
        'PASSWORD': os.getenv('DB_PASSWORD', 'mypassword'),
        'HOST': os.getenv('DB_HOST', 'localhost'),
        'PORT': os.getenv('DB_PORT', '5432'),
    }
}

Test Database Configuration

# Test environment database configuration
if 'test' in sys.argv:
    DATABASES['default'] = {
        'ENGINE': 'django.db.backends.sqlite3',
        'NAME': ':memory:',
    }

Connection Pool Configuration

For production environments, consider using connection pooling:

# Using django-db-connections for connection pool configuration
DATABASES = {
    'default': {
        'ENGINE': 'django_db_connections.backends.postgresql',
        'NAME': 'mydatabase',
        'USER': 'myuser',
        'PASSWORD': 'mypassword',
        'HOST': 'localhost',
        'PORT': '5432',
        'OPTIONS': {
            'pool_size': 20,
            'max_overflow': 10,
            'timeout': 30,
        }
    }
}

Best Practices

1. Use environment variables: Don't hardcode database credentials in code
2. Use SQLite for development: Convenient for development and testing
3. Use PostgreSQL for production: More powerful features and better performance
4. Configure connection pooling: Improve database connection efficiency
5. Regular backups: Ensure data security
6. Monitor database performance: Use tools like Django Debug Toolbar

Common Problem Solutions

Connection timeout issue:

DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.postgresql',
        # ... other configurations
        'OPTIONS': {
            'connect_timeout': 10,
        }
    }
}

Character set issue:

DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.mysql',
        # ... other configurations
        'OPTIONS': {
            'charset': 'utf8mb4',
            'init_command': "SET NAMES 'utf8mb4'",
        }
    }
}

Summary

Database configuration is an important foundation for Django applications:

1. ✅ Supports multiple database backends (PostgreSQL, MySQL, SQLite, Oracle)
2. ✅ Flexible single and multiple database configurations
3. ✅ Protect sensitive information through environment variables
4. ✅ Use database routing to implement read/write separation
5. ✅ Configure connection pooling to improve performance

Proper database configuration can ensure the stability, security, and performance of applications.

Next

We will learn about Django's migration system and how to manage database schema changes.

5.2 Data Migration →

Contents

Back to Course Outline