![]() Hipp based the syntax and semantics on those of PostgreSQL 6.5. In August 2000, version 1.0 of SQLite was released, with storage based on gdbm (GNU Database Manager). In September 2001, SQLite 2.0 replaced gdbm with a custom B-tree implementation, adding transaction capability. In June 2004, SQLite 3.0 added internationalization, manifest typing, and other major improvements, partially funded by America Online. In 2011, Hipp announced his plans to add a NoSQL interface to SQLite, as well as announcing UnQL, a functional superset of SQL designed for document-oriented databases. SQLite is one of four formats recommended for long-term storage of datasets approved for use by the Library of Congress. 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 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.ĭue to the server-less design, SQLite applications require less configuration than client–server databases. SQLite is called zero-conf because it does not require service management (such as startup scripts) or access control based on GRANT and passwords. Access control is handled by means of file-system permissions given to the database file itself. Databases in client–server systems use file-system permissions that give access to the database files only to the daemon process.Īnother implication of the serverless design is that several processes may not be able to write to the database file. In server-based databases, several writers will all connect to the same daemon, which is able to handle its locks internally. SQLite, on the other hand, has to rely on file-system locks. It has less knowledge of the other processes that are accessing the database at the same time. Therefore, SQLite is not the preferred choice for write-intensive deployments. However, for simple queries with little concurrency, SQLite performance profits from avoiding the overhead of passing its data to another process. SQLite uses PostgreSQL as a reference platform. "What would PostgreSQL do" is used to make sense of the SQL standard. ![]() One major deviation is that, with the exception of primary keys, SQLite does not enforce type checking the type of a value is dynamic and not strictly constrained by the schema (although the schema will trigger a conversion when storing, if such a conversion is potentially reversible). SQLite implements most of the SQL-92 standard for SQL, but lacks some features. For example, it only partially provides triggers and cannot write to views (however, it provides INSTEAD OF triggers that provide this functionality). Its support of ALTER TABLE statements is limited. SQLite uses an unusual type system for a SQL-compatible DBMS: instead of assigning a type to a column as in most SQL database systems, types are assigned to individual values in language terms it is dynamically typed. ![]()
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