What is SQLite?
To define in an simple manner, SQLite is an in-process library that implements a self-contained, serverless, zero-configuration, transactional SQL database engine.
SQLite is a relational database management system contained in a C programming library. In contrast to other database management systems, SQLite is not a separate process that is accessed from the client application, but an integral part of it.
SQLite is a popular choice as embedded database for local/client storage in application software such as web browsers. It is arguably the most widely deployed database engine, as it is used today by several widespread browsers, operating systems, and embedded systems, among others. SQLite has many bindings to programming languages.
Unlike client–server database management systems, the SQLite engine has no standalone processes with which the application program communicates. Instead, the SQLite library is linked in and thus becomes an integral part of the application program. The library can also be called dynamically. The application program uses SQLite’s functionality through simple function calls, which reduce latency in database access: function calls within a single process are more efficient than inter-process communication. SQLite stores the entire database (definitions, tables, indices, and the data itself) as a single cross-platform file on a host machine. It implements this simple design by locking the entire database file during writing. SQLite read operations can be multitasked, though writes can only be performed sequentially.
In the simplest terms, SQLite is a public-domain software package that provides a relational database management system, or RDBMS. Relational database systems are used to store user-defined records in large tables. In addition to data storage and management, a database engine can process complex query commands that combine data from multiple tables to generate reports and data summaries. Other popular RDBMS products include Oracle Database, IBM’s DB2, and Microsoft’s SQL Server on the commercial side, with MySQL and PostgreSQL being popular open source products.
The “Lite” in SQLite does not refer to its capabilities. Rather, SQLite is lightweight when it comes to setup complexity, administrative overhead, and resource usage. SQLite is defined by the following features:
SQLite does not require a separate server process or system to operate. The SQLite library accesses its storage files directly.
No server means no setup. Creating an SQLite database instance is as easy as opening a file.
The entire database instance resides in a single cross-platform file, requiring no administration.
A single library contains the entire database system, which integrates directly into a host application.
Small Runtime Footprint
The default build is less than a megabyte of code and requires only a few megabytes of memory. With some adjustments, both the library size and memory use can be significantly reduced.
SQLite transactions are fully ACID-compliant, allowing safe access from multiple processes or threads.
SQLite supports most of the query language features found in the SQL92 (SQL2) standard.
The SQLite development team takes code testing and verification very seriously.
Overall, SQLite provides a very functional and flexible relational database environment that consumes minimal resources and creates minimal hassle for developers and users.
Don’t be deceived into thinking that Sqlite is only for testing and development. For example, it works fine for websites receiving up to 100,000 hits a day– and this is a conservative limit. The maximum size for a Sqlite database is 140 Terabytes (which should be enough, right?), and it can be substantially faster than a full-blown RDBMS. The full database and all other necessary data is stored in a normal file in the host’s file system, so no separate server process is needed (cutting out all need for slow inter-process communication).
It’s good for situations where you don’t have access to a “real” database and still want the power of a relational db. For example, Firefox stores a bunch of information about your settings/history/etc in an SQLite database. You can’t expect everyone that runs firefox to have MySQL or postgre installed on their machine.