What is SQLite?

SQLite is an in-process library that implements a self-contained, serverless, zero-configuration, transactional SQL database engine. The code for SQLite is in the public domain and is thus free for use for any purpose, commercial or private. SQLite is the most widely deployed database in the world with more applications than we can count, including several high-profile projects.

SQLite is an embedded SQL database engine. Unlike most other SQL databases, SQLite does not have a separate server process. SQLite reads and writes directly to ordinary disk files. A complete SQL database with multiple tables, indices, triggers, and views, is contained in a single disk file. The database file format is cross-platform - you can freely copy a database between 32-bit and 64-bit systems or between big-endian and little-endian architectures. These features make SQLite a popular choice as an Application File Format. SQLite database files are a recommended storage format by the US Library of Congress. Think of SQLite not as a replacement for Oracle but as a replacement for fopen()

SQLite is a compact library. With all features enabled, the library size can be less than 750KiB, depending on the target platform and compiler optimization settings. (64-bit code is larger. And some compiler optimizations such as aggressive function inlining and loop unrolling can cause the object code to be much larger.) There is a tradeoff between memory usage and speed. SQLite generally runs faster the more memory you give it. Nevertheless, performance is usually quite good even in low-memory environments. Depending on how it is used, SQLite can be faster than direct filesystem I/O.

SQLite is very carefully tested prior to every release and has a reputation for being very reliable. Most of the SQLite source code is devoted purely to testing and verification. An automated test suite runs millions and millions of test cases involving hundreds of millions of individual SQL statements and achieves 100% branch test coverage. SQLite responds gracefully to memory allocation failures and disk I/O errors. Transactions are ACID even if interrupted by system crashes or power failures. All of this is verified by the automated tests using special test harnesses which simulate system failures. Of course, even with all this testing, there are still bugs. But unlike some similar projects (especially commercial competitors) SQLite is open and honest about all bugs and provides bugs lists and minute-by-minute chronologies of code changes.

The SQLite code base is supported by an international team of developers who work on SQLite full-time. The developers continue to expand the capabilities of SQLite and enhance its reliability and performance while maintaining backwards compatibility with the published interface spec, SQL syntax, and database file format. The source code is absolutely free to anybody who wants it, but professional support is also available.

The SQLite project was started on 2000-05-09. The future is always hard to predict, but the intent of the developers is to support SQLite through the year 2050. Design decisions are made with that objective in mind.

We the developers hope that you find SQLite useful and we entreat you to use it well: to make good and beautiful products that are fast, reliable, and simple to use. Seek forgiveness for yourself as you forgive others. And just as you have received SQLite for free, so also freely give, paying the debt forward.

SQLite is a software library that provides a relational database management system (RDBMS). Unlike most other database management systems, SQLite is serverless and self-contained, meaning it doesn't operate as a separate server process but is embedded directly into the application. It is a C library that provides a lightweight disk-based database that doesn't require a separate server process and allows access to the database using a nonstandard variant of the SQL query language.

Key features of SQLite include:

1. Serverless: As mentioned, SQLite does not operate as a separate server process. The entire database is a single ordinary file on disk.

2. Self-contained: The SQLite library is a self-contained, zero-configuration database engine. This makes it easy to deploy and use.

3. Cross-platform: SQLite is designed to be cross-platform and can run on various operating systems, including Windows, macOS, Linux, and others.

4. Transactional: SQLite is ACID-compliant (Atomicity, Consistency, Isolation, Durability), providing reliable transactions.

5. Single-user: SQLite is well-suited for single-user applications and embedded systems where simplicity and a small footprint are important.

6. Lightweight: It is designed to be lightweight, both in terms of resource usage and the library size.

7. Open source: SQLite is open-source software, and its source code is in the public domain, making it freely available for use and distribution.

SQLite is commonly used in various applications, including mobile apps, desktop software, embedded systems, and more, where a lightweight, self-contained, and easy-to-use database solution is needed. It is not as suitable for large-scale, high-concurrency scenarios compared to some other database management systems like MySQL or PostgreSQL, but it excels in its simplicity and ease of integration.