SQLite Database (.sqlite, .db)

Overview

SQLite is a C-language library that implements a small, fast, self-contained, high-reliability, full-featured SQL database engine. SQLite databases are fully self-contained, requiring no external dependencies or server setup. They are stored as single cross-platform disk files that can be freely copied between 32-bit and 64-bit systems or between big-endian and little-endian architectures.

Technical Specifications

Format Details

• File Extension: .sqlite, .db, .sqlite3, .db3
• MIME Type: application/vnd.sqlite3
• Database Type: Relational database
• Architecture: Serverless, zero-configuration

Key Characteristics

• ACID Transactions: Full ACID compliance
• File Format: Single cross-platform database file
• Encoding: UTF-8, UTF-16 (little/big endian)
• Maximum Database Size: 281 TB
• Maximum Row Size: 1 GB
• Maximum Column Count: 2000

History and Development

SQLite was first released in August 2000 by D. Richard Hipp. Key milestones:

• 2000: Initial release (SQLite 1.0)
• 2004: SQLite 3.0 with major format changes
• 2010: Write-Ahead Logging (WAL) mode introduced
• 2013: Common Table Expressions (CTE) added
• 2018: Window functions support
• 2021: STRICT tables and generated columns

Common Use Cases

Mobile Applications

-- Creating a simple mobile app database
CREATE TABLE users (
    id INTEGER PRIMARY KEY,
    username TEXT UNIQUE NOT NULL,
    email TEXT UNIQUE NOT NULL,
    created_at DATETIME DEFAULT CURRENT_TIMESTAMP
);

CREATE TABLE posts (
    id INTEGER PRIMARY KEY,
    user_id INTEGER,
    content TEXT NOT NULL,
    created_at DATETIME DEFAULT CURRENT_TIMESTAMP,
    FOREIGN KEY (user_id) REFERENCES users(id)
);

Desktop Applications

-- Configuration storage
CREATE TABLE app_settings (
    key TEXT PRIMARY KEY,
    value TEXT,
    type TEXT DEFAULT 'string'
);

INSERT INTO app_settings VALUES 
    ('theme', 'dark', 'string'),
    ('auto_save', '1', 'boolean'),
    ('max_files', '100', 'integer');

Data Analysis

-- Analytics queries with window functions
SELECT 
    date,
    sales,
    SUM(sales) OVER (ORDER BY date ROWS BETWEEN 6 PRECEDING AND CURRENT ROW) as rolling_7_day
FROM daily_sales
ORDER BY date;

Tools and Software

Command Line Tools

• sqlite3: Official command-line interface
• sqlite3_analyzer: Database analysis tool
• sqlitebrowser: GUI database browser

Programming Language Support

# Python
import sqlite3

conn = sqlite3.connect('example.db')
cursor = conn.cursor()
cursor.execute("SELECT * FROM users")
results = cursor.fetchall()
conn.close()

// Node.js
const Database = require('better-sqlite3');
const db = new Database('example.db');

const stmt = db.prepare('SELECT * FROM users WHERE id = ?');
const user = stmt.get(1);
db.close();

// C#
using Microsoft.Data.Sqlite;

using var connection = new SqliteConnection("Data Source=example.db");
connection.Open();

var command = connection.CreateCommand();
command.CommandText = "SELECT * FROM users";
using var reader = command.ExecuteReader();

GUI Applications

• DB Browser for SQLite: Cross-platform GUI
• SQLiteStudio: Advanced database management
• DBeaver: Universal database tool
• DataGrip: JetBrains database IDE

Technical Features

Storage Classes

-- SQLite's dynamic typing system
CREATE TABLE example (
    id INTEGER,           -- Integer storage class
    name TEXT,           -- Text storage class
    price REAL,          -- Real storage class
    data BLOB,           -- Blob storage class
    is_active            -- Can store any type
);

Advanced Features

-- JSON support (SQLite 3.38+)
CREATE TABLE products (
    id INTEGER PRIMARY KEY,
    name TEXT,
    metadata JSON
);

INSERT INTO products VALUES (1, 'Widget', '{"color": "red", "size": "large"}');
SELECT json_extract(metadata, '$.color') FROM products;

-- Full-text search
CREATE VIRTUAL TABLE documents USING fts5(title, content);
INSERT INTO documents VALUES ('SQLite Guide', 'Complete SQLite documentation...');
SELECT * FROM documents WHERE documents MATCH 'sqlite';

Performance Optimization

-- Indexing
CREATE INDEX idx_user_email ON users(email);
CREATE INDEX idx_posts_user_date ON posts(user_id, created_at);

-- Analyze for query optimization
ANALYZE;

-- Vacuum to reclaim space
VACUUM;

Best Practices

Database Design

• Use appropriate data types despite dynamic typing
• Create indexes for frequently queried columns
• Use foreign key constraints for referential integrity
• Normalize data appropriately

Performance

• Enable WAL mode for better concurrency
• Use prepared statements to prevent SQL injection
• Batch multiple operations in transactions
• Use EXPLAIN QUERY PLAN to optimize queries

Backup and Maintenance

-- Backup database
.backup main backup.db

-- Check database integrity
PRAGMA integrity_check;

-- Optimize database
PRAGMA optimize;

Security Considerations

Access Control

• SQLite has no built-in user authentication
• File-level permissions control access
• Encrypt sensitive databases at file system level

SQL Injection Prevention

# Bad - vulnerable to SQL injection
cursor.execute(f"SELECT * FROM users WHERE name = '{user_input}'")

# Good - using parameterized queries
cursor.execute("SELECT * FROM users WHERE name = ?", (user_input,))

Data Encryption

• Use SQLCipher for encrypted SQLite databases
• Consider application-level encryption for sensitive data
• Secure file permissions and storage location

Comparison with Other Databases

Feature	SQLite	MySQL	PostgreSQL
Setup	Zero-config	Server required	Server required
Concurrency	Limited writes	High	High
Size Limit	281 TB	No limit	No limit
ACID	Full	Full	Full
Use Case	Embedded/Local	Web applications	Enterprise

File Format Variants

• SQLite 3: Current format (since 2004)
• SQLite 2: Legacy format (compatibility mode)
• WAL files: Write-Ahead Log files (.wal)
• SHM files: Shared memory files (.shm)

SQLite remains one of the most widely deployed database engines worldwide, found in every Android device, iPhone, web browser, and countless desktop applications due to its reliability, simplicity, and zero-configuration design.