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New databases Databases can be created via commands[[Commands]], via [[XQuery]], in the [[GUI]], or and with any of ourvarious [[Developing|APIs]]. If some an initial input is specified along with the a create operation, it some time can be saved, as the specified resources will be added to the database in a bulk operation:
Database must follow the The database name is composed of a restricted set of characters (see [[Valid Names|valid names constraints]]).Various [[parsersParsers]] can be chosen selected to influence control the database creationimport process, or to convert data of different formats input type to XML. '''Note:''' A main-memory only database can be created using the the <code>SET MAINMEM true</code> command before calling <code>CREATE DB</code> ([[Databases#In Memory Database|see below]] for more).
==HTTP Services==With {{Function|Database|db:get-value}}, XQuery values can be retrieved. In the following example, we assume that an XQuery map {{Code|cities}} was stored in an {{Code|indexes}} database:
* With [[REST]] and [[WebDAV]], all database resources can be requested in a uniform way<syntaxhighlight lang="xquery">let $city-map := db:get-value('indexes', no matter if they are well'cities')return $city-formed XML documents or binary files.map?Chile</syntaxhighlight>
The [[Options#AUTOFLUSH{{Option|AUTOFLUSH]] option }} can be turned off before ''bulk operations'' (i.e. , before a large number of numerous new resources is are added to the database).
The [[Options#ADDCACHEIf {{Option|ADDCACHE]] option will first cache }} is enabled, the input will be cached before adding it is added to the database. This is helpful when the input documents to be added are expected to eat up consume too much main -memory.
The With the following commands create [[Commands#Command Scripts|command script]], an empty databaseis created, add two resourcesare added (one directly, explicitly flush data structures to diskanother one cached), and finally delete all inserted datais exported to the file system:
STORE BINARY PUT TO images/ 123.jpgFLUSHDELETE EXPORT /path/to/file-system/
Last but not least* Commands: {{Command|EXPORT}} writes all resources to the specified target directory.* GUI: Go to ''Database'' → ''Export'', XML documents can also be added via choose the GUI target directory and the press ''DatabaseOK'' menu.* XQuery: Use {{Function|Database|db:export}}.* WebDAV: Locate the database directory (or a subdirectory of it) and copy all contents to another location.
All resources stored A database can be created in main-memory by enabling the {{Option|MAINMEM}} option. Next, in the standalone context, a main-memory database can be ''exported''created, i.e., written back to disk. This which can then be done in several ways:accessed by subsequent commands.
* Commands: <code>If a BaseX server is started, and if a database is created in its context at startup time, e.g., with the [[Commands#EXPORTCommand-Line Options|EXPORTcommand-line option -c]]</code> writes all resources to the specified target directory* GUI: Go to ''Database'' → ''Export''and a {{Command|CREATE DB}} call, choose the target directory BaseX clients can then access and press ''OK''* WebDAVupdate this database: Locate the database directory (or a sub-directory of it) and copy all contents to another location
* In the standalone context, a main-memory database can be created (using <code>CREATE DB</code>), which can then be accessed by subsequent commands# ClientbasexclientUsername: ...* If a BaseX server instance is started, and if a database is created in its context (using <code>CREATE DB</code>), other BaseX client instances can access (and update) this database (using OPEN, dbPassword:open, etc.) as long as no other database is opened/created by the server..* You can force an ordinary database BaseX [Client]Try 'help' to being copied to memory by using <codeget more information.>XQUERY count(db:openget('some-dbmainmem') update {}//*)1876462Query executed in 0.97 ms.</codesyntaxhighlight>
'''NoteAdditional notes:''' * You can force an ordinary database, or parts of it, to being temporarily copied to memory by applying an empty [[XQuery_Update#Main-Memory_Updates|main-memory update]] on a database instances are also created by the invocation of node: <code>docdb:get(...'some-db')update { }</code>* If you open local or remote documents with <code>fn:doc</code> or <code>fn:collection(...)</code>, if the argument resulting internal representation is not aidentical to those of main-memory database instances (no matter regardless of which value is set for {{Option|MAINMEM}}). In other words:the same internal representation is used for main-memory databases anddocuments/collections generated via XQuery.
→Changelog
This page is part of the [[Getting Started]] Section.
In BaseX, a ''database'' is a pretty light-weight concept and can be comparedto a ''collection''. It contains an arbitrary number of may contain one or more '''resources''',which are addressed by their a unique database path. Resources There is no explicit layer for collections: Instead, collections are implicitly created and deleted, and collections result from the existence of documents in specific paths. As a single database is restricted to 2 billion XML nodes (see [[Statistics]]), but resources can easily be distributed across multiple database instances. Multiple databases can either beaddressed (queried, updated) by a single XQuery expression. Three different resource types exist: {|class="wikitable"|- valign="top"| '''XML documentsResource Type''' or | '''raw filesDescription''' (binaries)|- valign="top"| XML Documents| The default resource type. The storage and index features are optimized for XML contents, or any other contents stored in an XML representation.Some information on |- valign="top"| Binary Data| Binary data: Raw data of any type, stored in its binary representation. See [[Binary Data]] for more information.|- valign="top"| XQuery Values| Introduced with {{Announce|Version 10}}: Results of XQuery expressions, stored in a binary datarepresentation for fast retrieval. All value types are supported, including maps and arrays, but excluding any other [[Higher-Order Functions#Function Items|function items]] can be found on an extra page.|}
=Create Databases=
* [[Startup#BaseX Standalone|ConsoleCommand-Line]]: <code>CREATE DB db documents /path/to/resources</code> will add initial documents : Add resources in the specified path to a databasenamed {{Code|documents}}.* [[Startup#BaseX GUI|GUI]]: Go to ''Database'' → ''New'', press ''BrowseBrowse…'' to choose an initial file or directory, and press ''OK''.
=Access Resources=
{| class="wikitable"
|-valign="top"
!Function
!Example
!Description
|-valign="top"|[[{{Function|Database Module#db:open|db:open]]get}}|{{Code|db:openget("db", "path/to/docs")}}
|Returns all documents that are found in the database {{Code|db}} at the (optional) path {{Code|path/to/docs}}.
|-valign="top"|<code>[http://www.xqueryfunctions.com/xq/fn_collection.html fn:collection]</code>
|{{Code|collection("db/path/to/docs")}}
|Returns all documents at the location {{Code|path/to/docs}} in the database {{Code|db}}.<br/>If no path is specified after the database, all documents in the database will be returned.<br/>If no argument is specified, all documents of the database will be returned that has been opened in the global context.
|-valign="top"|<code>[http://www.xqueryfunctions.com/xq/fn_doc.html fn:doc]</code>
|{{Code|doc("db/path/to/doc.xml")}}
|Returns the document at the location {{Code|path/to/docs}} in the database {{Code|db}}.<br/>An error is raised if the specified yields zero or more than one document.
You can access multiple databases in a single query:
<pre classsyntaxhighlight lang="brush:xquery">
for $i in 1 to 100
return db:openget('books' || $i)//book/title</presyntaxhighlight>
If the [[Options#DEFAULTDB{{Option|DEFAULTDB]] }} option is turned on, the path argument of the {{Code|fn:doc}} or {{Code|fn:collection}} function functions will first be resolved against the globally opened database.
Two more functions are available for retrieving information on database nodes:
!Example
!Description
|-valign="top"|[[{{Function|Database Module#db:name|db:name]]}}
|{{Code|db:name($node)}}
|Returns the name of the database in which the specified {{Code|$node}} is stored.
|-valign="top"|[[{{Function|Database Module#db:path|db:path]]}}
|{{Code|db:path($node)}}
|Returns the path of the database document in which the specified {{Code|$node}} is stored.
The {{Code|fn:document-uri}} and {{Code|fn:base-uri}} functions return URIs that can also be reused as arguments for the {{Code|fn:doc}} and {{Code|fn:collection}} functions. As a result, the following example query always returns {{Code|true}}:
<pre classsyntaxhighlight lang="brush:xquery">
every $c in collection('anyDB')
satisfies doc-available(document-uri($c))
</presyntaxhighlight>
If the argument of {{Code|fn:doc}} or {{Code|fn:collection}} does not start with a valid database name, or if the addressed database does not exist, the string is interpreted as URI reference, and the documents found at this location will be returned. Examples:
* {{Code|doc("http://web.de")}}: retrieves the addressed URI and returns it as a main-memory document node.
* {{Code|doc("myfile.xml")}}: retrieves the given file from the file system and returns it as a main-memory document node. Note that updates to main-memory nodes are not automatically written back to disk unless the <code>[[Options#WRITEBACK{{Option|WRITEBACK]]</code> }} option is set.
* {{Code|collection("/path/to/docs")}}: returns a main-memory collection with all XML documents found at the addressed file path.
==Raw FilesBinary Data==
The <code>[[Commands#RETRIEVE{{Command|RETRIEVE]]</code> BINARY GET}} command and the <code>[[{{Function|Database Module#db:retrieve|db:retrieve]]</code> get-binary}} function can be used to return files in their native byte representation.
If the API you use does not support binary output (this which is e.g. the case for various [[Clients|Client]] language bindings), you need to can convert your binary data to its string representation before returning it to the client:
<pre classsyntaxhighlight lang="brush:xquery">string(db:retrieveget-binary('multimedia', 'sample.avi'))</presyntaxhighlight> ==XQuery Values==
=Update Resources=
==Commands==
Once you have created a database, additional commands exist to modify its contents:
* XML documents can be added with the <code>[[Commands#ADD{{Command|PUT}} and {{Command|ADD]]</code> command.* Raw files are added with <code>[[Commands#STORE|STORE]]</code>}} commands.* Existing resources can be replaced Binary data is stored with the <code>[[Commands#REPLACE{{Command|REPLACE]]</code> commandBINARY PUT}}.* Resources of all types can be deleted via <code>[[Commands#DELETE{{Command|DELETE]]</code>}}.
<pre>
SET ADDCACHE true
ADD /path/to/xml/documents
</pre>
==XQuery== You may as well can also use functions from the BaseX-specific [[Database Module|XQuery Database Functions]] to create, add, replace, and or delete XML documents:
<pre classsyntaxhighlight lang="brushxquery">db:add('documents', '/path/to/xml/resources/')</syntaxhighlight> Function from other modules, such as the [[File Module]], can be utilized to filter the input. With the following code, all files that contain numbers in the filename are selected, and stored as XML. If an input file contains no well-formed XML, it is stored as binary resource, and the error message is stored as a string value: <syntaxhighlight lang="xquery">let $db := 'documents'let $root := "'/path/to/xmlresources/documents/"'for $file path in file:list($root)where matches($path, '\d+')return try { db:put($db, fetch:doc($root || $path), $path)} catch * { db:put-binary($db, $root || $path, $path), db:addput-value($db, $err:description, $path || '.error')}</syntaxhighlight> The error messages can e.g. be analyzed in a second step: <syntaxhighlight lang="databasexquery">let $errors := db:get-value('documents')for $filename in map:keys($errors)where ends-with($filename, '.error')return $root filename || ': ' || $fileerrors?($filename)</presyntaxhighlight> =Export Database= All resources stored in a database can be ''exported'', i.e., written back to disk, e.g., as follows:
=Export DataMain-Memory Databases=
<syntaxhighlight lang=In Memory "perl"># Serverbasexserver -c"SET mainmem on" -c"CREATE DB mainmem document.xml"BaseX [Server]Server was started (port: 1984).MAINMEM: trueDatabase='mainmem' created in 1782.80 ms.
=Changelog=
;Version 10.0
* Added: New resource type for XQuery values.
;Version 8.4
* Updated: [[#Raw Files|Raw Files]]: Items of binary type can be output without specifying the obsolete <code>raw</code> serialization method.
;Version 7.2.1
* Updated: {{Code|fn:document-uri}} and {{Code|fn:base-uri}} now return strings that can be reused with {{Code|fn:doc}} or {{Code|fn:collection}} to reopen the original document.
