SQLite/Printable version
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Introduction
Design
[edit | edit source]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.
Due to the server-less design, SQLite applications require less configuration than client-server databases. SQLite is called zero-conf[1] 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 which give access to the database files only to the daemon process.
Another 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.[2] 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.[3][4] 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 strives to follow Postel's Rule.[5]
History
[edit | edit source]D. Richard Hipp designed SQLite in the spring of 2000 while working for General Dynamics on contract with the United States Navy.[6] Hipp was designing software used aboard guided missile destroyers, which originally used HP-UX with an IBM Informix database back-end. SQLite began as a Tcl extension.[7]
The design goals of SQLite were to allow the program to be operated without installing a database management system or requiring a database administrator. 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). SQLite 2.0 replaced gdbm with a custom B-tree implementation, adding transaction capability. SQLite 3.0, partially funded by America Online, added internationalization, manifest typing, and other major improvements.
In 2011 Hipp announced his plans to add a NoSQL interface (managing documents expressed in JSON) to SQLite databases and to develop UnQLite, an embeddable document-oriented database.[8]. UnQLite was released as an independent database.[9]
Features
[edit | edit source]SQLite implements most of the SQL-92 standard for SQL but it lacks some features. For example, it partially provides triggers, and it cannot write to views (however it provides INSTEAD OF triggers that provide this functionality). While it provides complex queries, it still has limited ALTER TABLE function, as it cannot modify or delete columns.[10]
SQLite uses an unusual type system for an 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. Moreover, it is weakly typed in some of the same ways that Perl is: one can insert a string into an integer column (although SQLite will try to convert the string to an integer first, if the column's preferred type is integer). This adds flexibility to columns, especially when bound to a dynamically typed scripting language. However, the technique is not portable to other SQL products. A common criticism is that SQLite's type system lacks the data integrity mechanism provided by statically typed columns in other products. The SQLite web site describes a "strict affinity" mode, but this feature has not yet been added.[5] However, it can be implemented with constraints like CHECK(typeof(x)='integer')
.[6]
SQLite with full Unicode function is optional.[11]
Several computer processes or threads may access the same database concurrently. Several read accesses can be satisfied in parallel. A write access can only be satisfied if no other accesses are currently being serviced. Otherwise, the write access fails with an error code (or can automatically be retried until a configurable timeout expires). This concurrent access situation would change when dealing with temporary tables. This restriction is relaxed in version 3.7 when write-ahead logging (WAL) is turned on enabling concurrent reads and writes.[12]
SQLite version 3.7.4 first saw the addition of the FTS4 (full text search) module, which features enhancements over the older FTS3 module.[13] FTS4 allows users to perform full text searches on documents similar to how search engines search webpages.[14] Version 3.8.2 added support for creating tables without rowid,[15] which may provide space and performance improvements.[16] Common table expressions support was added to SQLite in version 3.8.3.[17]
In 2015, with the json1 extension[18] and new subtype interfaces, SQLite version 3.9 introduced JSON content managing.
Development and distribution
[edit | edit source]SQLite's code is hosted with Fossil, a distributed version control system that is itself built upon an SQLite database.[19]
A standalone command-line program is provided in SQLite's distribution. It can be used to create a database, define tables, insert and change rows, run queries and manage an SQLite database file. It also serves as an example for writing applications that use the SQLite library.
SQLite uses automated regression testing prior to each release. Over 2 million tests are run as part of a release's verification. Starting with the August 10, 2009 release of SQLite 3.6.17, SQLite releases have 100% branch test coverage, one of the components of code coverage. The tests and test harnesses are partially public domain and partially proprietary.[20]
Notable users
[edit | edit source]- The browsers Google Chrome, Opera, Safari and the Android Browser all allow for storing information in, and retrieving it from, a SQLite database within the browser, using the Web SQL Database technology, although this is rapidly becoming deprecated (namely superseded by IndexedDB).
- Mozilla Firefox and Mozilla Thunderbird store a variety of configuration data (bookmarks, cookies, contacts etc.) in internally managed SQLite databases. There is a third-party add-on that uses the code supporting this functionality to provide a user interface for managing arbitrary SQLite databases.[21]
- Various web application frameworks
- Adobe Systems uses SQLite as its file format in Adobe Photoshop Lightroom, a standard database in Adobe AIR, and internally within Adobe Reader.[7]
- Evernote uses SQLite to store its local database repository in Windows.
- Skype[22]
- Apple[23] adopted it as an option in macOS's Core Data API from the original implementation in Mac OS X 10.4 onwards, and also for administration of videos and songs, and in iOS for storage of text messages on the iPhone.
- Windows 10[24]
Programming language support
[edit | edit source]A large number of programming languages provide bindings for SQLite, including:
- AutoIt[25]
- various dialects of BASIC including FreeBASIC, PureBasic, RFO BASIC!, Visual Basic and Xojo
- C
- C#
- C++
- Clipper//Harbour
- Curl
- D
- Elixir
- Emacs Lisp[26]
- F#[27]
- Go
- Haskell
- Haxe
- Java (on JVM and DVM)
- JavaScript[28]
- Julia
- distributions of Lisp such as Common Lisp, newLisp, OpenLisp
- Transcript (on LiveCode)
- LabVIEW
- Lua
- MATLAB
- Nim
- Objective-C (on macOS and iOS)
- OCaml
- several flavours of Pascal including Free Pascal, Component Pascal and Delphi
- Perl[29]
- PHP
- Pike
- Python[30]
- R
- Racket[31]
- REBOL
- Ruby[32]
- Scheme
- Smalltalk
- Swift (on macOS and iOS)
- Tcl
- Xojo
References
[edit | edit source]Citations
[edit | edit source]- ↑ "SQLite Is A Zero-Configuration Database". SQLite.org. Retrieved August 3, 2015.
- ↑ "Appropriate Uses For SQLite". SQLite.org. Retrieved 2015-09-03.
- ↑ "PGCon 2014: Clustering and VODKA". Lwn.net. Retrieved 2017-01-06.
- ↑ "PGCon2014: SQLite: Protégé of PostgreSQL". Pgcon.org. Retrieved 2017-01-06.
- ↑ a b "SQLite: StrictMode". Sqlite.org. Retrieved September 3, 2015.
- ↑ a b Owens, Michael (2006). The Definitive Guide to SQLite. Apress. doi:10.1007/978-1-4302-0172-4_1. ISBN 978-1-59059-673-9.
- ↑ a b "Well-Known Users Of SQLite". SQLite. Retrieved August 5, 2015.
- ↑ "Interview: Richard Hipp on UnQL, a New Query Language for Document Databases". InfoQ. August 4, 2011. Retrieved October 5, 2011.
- ↑ UnQLite FAQ
- ↑ "SQL Features That SQLite Does Not Implement". SQLite.org. January 1, 2009. Retrieved October 14, 2009.
- ↑ "Case-insensitive matching of Unicode characters does not work". SQLite Frequently Asked Questions. Retrieved 2015-09-03.
- ↑ "Write Ahead Logging in SQLite 3.7". SQLite.org. Retrieved September 3, 2011.
WAL provides more concurrency as readers do not block writers and a writer does not block readers. Reading and writing can proceed concurrently
- ↑ "SQLite Release 3.7.4 On 2010-12-08". SQLite.org. December 8, 2010. Retrieved September 3, 2015.
- ↑ "SQLite FTS3 and FTS4 Extensions". SQLite.org. Retrieved September 3, 2015.
- ↑ "SQLite Release 3.8.2 On 2013-12-06". SQLite.org. December 6, 2013. Retrieved September 3, 2015.
- ↑ "The WITHOUT ROWID Optimization". SQLite.org. Retrieved September 3, 2015.
- ↑ "SQLite Release 3.8.3 On 2014-02-03". SQLite.org. February 3, 2014. Retrieved September 3, 2015.
- ↑ https://sqlite.org/json1.html
- ↑ "Fossil: Fossil Performance". Fossil-scm.org. August 23, 2009. Retrieved September 12, 2009.
- ↑ "How SQLite Is Tested". SQLite.org. Retrieved September 12, 2009.
- ↑ "SQLite Manager :: Add-ons for Firefox". Addons.mozilla.org. 2015-02-28. Retrieved 2017-01-06.
- ↑ "Skype client using SQLite?". Mail-archive.com. August 28, 2007. Retrieved June 14, 2010.
- ↑ "Show Download History List of All Files Ever Downloaded Within Mac OS X". Osxdaily.com. 2012-07-12. Retrieved 2017-01-06.
- ↑ "SQLite databases". Msdn.microsoft.com. 2016-09-19. Retrieved 2017-01-06.
- ↑ "User Defined Functions". Autoitscript.com. Retrieved 2017-01-06.
- ↑ "SQLite3 API for GNU Emacs 25+". github.com. Retrieved 2017-10-02.
- ↑ Ross McKinlay; Colin Bull. "SQLProvider". Fsprojects.github.io. Retrieved 2017-01-06.
- ↑ "Google Code Archive - Long-term storage for Google Code Project Hosting". Code.google.com. Retrieved 2017-01-06.
- ↑ Adam Kennedy. "DBD::SQLite - Self-contained RDBMS in a DBI Driver". Metacpan.org. Retrieved 2017-01-06.
- ↑ "PySqlite – The Trac Project". Trac.edgewall.org. 2015-12-31. Retrieved 2017-01-06.
- ↑ "Continue: Web Applications in Racket - 15 Using an SQL database". docs.racket-lang.org. Retrieved 2017-02-24.
- ↑ "Archived copy". Archived from the original on 2010-04-17. Retrieved 2010-04-03.
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Sources
[edit | edit source]- Allen, Grant; Owens, Mike (November 5, 2010). The Definitive Guide to SQLite (2nd ed.). Apress. p. 368. ISBN 1-4302-3225-0.
- Kreibich, Jay A. (August 17, 2010). Using SQLite (1st ed.). O'Reilly Media. p. 528. ISBN 0-596-52118-9.
- van der Lans, Rick F. (September 7, 2009). The SQL Guide to SQLite (1st ed.). lulu.com. p. 542. ISBN 0-557-07676-5.
- Newman, Chris (November 9, 2004). SQLite (Developer's Library) (1st ed.). Sams. p. 336. ISBN 0-672-32685-X.
Downloading and using
Downloading
[edit | edit source]All tools as well as the C-sources and HTML-documentation you need to install sqlite3 on your computer are packed together in an archiveFile on SQLite's downloadPage.
- In following files vv stands for version two digits following "3." uu=update (after ".vv.") and occasionally pp (usually 00) after ".uu."
As of now (12:31, 29 March 2020 (UTC)) vv=31, uu=01, pp=00
- Tools are stored in one or more files depending on your Operating System:
Android
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Linux
[edit | edit source]Mac OS X (x86)
[edit | edit source]Windows
[edit | edit source]Universal Windows Platform
[edit | edit source]Windows Phone 8
[edit | edit source]- Phone 8.0 VSIX package with an extension SDK VS2012 for SQLite3vvuupp
- Phone 8.1 VSIX package with an extension SDK VS2013 for SQLite3vvuupp
Windows Runtime
[edit | edit source]- Visual Studio 2012 VSIX package with an extension SDK WinRT for SQLite3vvuupp
- Visual Studio 2013 VSIX package with an extension SDK WinRT 8.1 for SQLite3vvuupp
.NET
[edit | edit source]Sources
[edit | edit source]- Amalgamation of SQLite3vvuupp
- Amalgamation of SQLite3vvuupp + TCL-configuration
Alternative sources
[edit | edit source]- not recommended
Beta sources
[edit | edit source]- Prerelease tarball of 3.32.0 on 26 March 2020
Documentation (HTML)
[edit | edit source]Using
[edit | edit source]After unzipping and moving the content of the folder(s) under a directory in your %PATH% (or $PATH) you can use the executable sqlite3 from anywhere within your computer system.
Questions?
[edit | edit source]For questions, requests etcetera there is a forum.
SQL standard divergences
Types
[edit | edit source]SQLite is dynamically typed. This means that as you fill columns the affinity depends on the content. Four data types exist except NULL: BLOB, INTEGER, REAL (aka FLOAT) and TEXT.[1]
References
[edit | edit source]- ↑ Result Values From A Query sqlite.org, SQLite C Interface, visited 7 May 2019
Release3
Before reading this you're supposed to have downloaded and unpacked in your PATH the latest version of the executable command line interface sqlite3 for your operating system.
CommandLine
[edit | edit source]Usage: sqlite3 [OPTIONS] FILENAME [SQL]
- FILENAME is the name of an SQLite database. A new database is created if the file does not previously exist.
- SQL is a dot-, SQL-command or Pragma. OPTIONS include:
-A ARGS... = .archive ARGS and exit -append append database to end of file -ascii = .mode ascii -bail = .bail on -batch force batch I/O -box = .mode box -column = .mode column -cmd COMMAND run "COMMAND" before reading stdin -csv = .mode csv -deserialize open using sqlite3_deserialize() -echo = .echo on -init FILENAME read/process named file -[no]header = .header [off] or on -help show this message -html = .mode HTML -interactive force interactive I/O -json = .mode json -line = .mode line |
-list = .mode list -lookaside SIZE N use N entries of SIZE bytes for lookaside memory -markdown = .mode markdown -memtrace trace all memory allocations and (de)allocations -mmap N default mmap size set to N -newline SEP = .separator "|" SEP. Default: "\n" -nofollow = refuse to open symbolic links to database files -nullvalue TEXT = .NULLvalue TEXT. Default "" -pagecache SIZE N use N slots of SIZE bytes each for page cache memory -quote = .mode quote -readonly open the database read-only -separator SEP = .separator SEP. Default: "|" -stats print memory stats before each finalize -table = .mode table -tabs = .mode tabs -version = .version -vfs NAME use NAME as the default VFS -zip open the file as a ZIP Archive |
DotCommands
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- D-notes
More info @sqlite.org/cli.html#special_commands_to_sqlite3_dot_commands_
a .ar [OPTION...] [FILE...] The .ar command manages sqlar archives. Examples: .ar -cf archive.sar foo bar # Create archive.sar from files foo and bar .ar -tf archive.sar # List members of archive.sar .ar -xvf archive.sar # Verbosely extract files from archive.sar Each command line must feature exactly one command option: -c, --create Create a new archive -u, --update Update or add files to an existing archive -t, --list List contents of archive -x, --extract Extract files from archive And zero or more optional options: -v, --verbose Print each filename as it is processed -f FILE, --file FILE Operate on archive FILE (default is current db) -a FILE, --append FILE Operate on FILE opened using the apndvfs VFS -C DIR, --directory DIR Change to directory DIR to read/extract files -n, --dryrun Show the SQL that would have occurred See also: sar-support e or invoke system text editor (-e) or spreadsheet (-x) on the output. |
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KeyWords
[edit | edit source]If one wants to use one of following words as an identifier the word needs to be enclosed in two double quotes '"', backquotes '`' or '[' and ']'.[1]
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- K-notes and/or references
- ↑ SQLite Keywords more info @sqlite.org/lang_keywords.html.
- ↑ a b Not a keyword, but a predefined variable. Usage as identifier might be confusing.
Pragmas
[edit | edit source]Pragmas are special commands to show or [change] behavior of open database[schema](s)
- Usage: PRAGMA [schema-name.]name [ = TEXT or INT ];
- active pragmas (61)
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- deprecated pragmas (7)
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- pragmas with non-standard compile-options (5)
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- More info: List Of PRAGMAs @SQLite.org