Chapter 1. Overview
SQLite provides a good framework in which you can define and use custom-made SQL functions,
aggregate functions, and collating sequences. It also supports UTF-8 and UTF-16 standards-based
encoding for Unicode text.
Cross-platform
SQLite lets you move database files between platforms. For example, you can create a database
on a Linux x86 machine, and use the same database (by making a copy) on an ARM platform
without any alterations. The database behaves identically on all supported platforms.
SQLite is different from most other modern SQL databases in the sense that its primary design goal is to be
simple. SQLite strives to be simple, even if it leads to occasional inefficient implementations of some
features. It is simple to maintain, customize, operate, administer, and embed in C applications. It uses simple
techniques to implement ACID properties.
SQLite supports a large subset of SQL-92 data definition and manipulation features, and some SQLite specific
commands. You can create tables, indexes, triggers, and views using standard data definition SQL constructs.
You can manipulate stored information using INSERT, DELETE, UPDATE, and SELECT SQL constructs. The
following is a list of additional features supported as of the SQLite 3.3.6 release (the latest set of supported
features can be obtained from the SQLite homepage):
● Partial support for ALTER TABLE (rename table, add column)
● UNIQUE, NOT NULL, CHECK constraints
● Subqueries, including correlated subqueries, INNER JOIN, LEFT OUTER JOIN, NATURAL JOIN, UNION,
UNION ALL, INTERSECT, EXCEPT
● Transactional commands: BEGIN, COMMIT, ROLLBACK
● SQLite commands, including reindex, attach, detach, pragma
The following SQL-92 features are not yet supported as of the SQLite 3.3.6 release:
● Foreign key constraints (parsed but not enforced)
● Many ALTER TABLE features
● Some TRIGGER-related features
● RIGHT and FULL OUTER JOIN
● Updating a VIEW
● GRANT and REVOKE
SQLite stores an entire database in a single, ordinary native file that can reside anywhere in a directory of the
native filesystem. Any user who has permission to read the file can read anything from the database. A user
who has write permission on the file and the container directory can change anything in the database. SQLite
uses a separate journal file to save transaction recovery information that is used in the event of transaction
aborts or system failures. The SQLite attach command helps a transaction work on multiple databases
simultaneously. Such transactions are also ACID-compliant. Pragma commands let you alter the behavior of
the SQLite library.
SQLite allows multiple applications to access the same database concurrently. However, it supports a limited
form of concurrency among transactions. It allows any number of concurrent read-transactions on a
database, but only one exclusive write-transaction.
SQLite is a successful RDBMS. It has been widely used in low-to-medium tier database applications such as
web site services (SQLite works fine with up to 100,000 evenly distributed hits a day; the SQLite
development team has demonstrated that SQLite may even withstand 1,000,000 hits a day), cell phones,
PDAs, set-top boxes, standalone appliances. You could even use it in teaching SQL to students in a beginner
database course. The source code itself is well documented and commented, and you can use it in advanced
database management courses, or in projects as a reference technology. It is available freely, and has no
licensing complications because it is in the public domain.
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