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This [[Module Library|XQuery Module]] contains functions for parsing and evaluating XQuery strings and modules at runtime, and to run code in parallel.

=Functions= This [[Module Library|XQuery Module]] contains functions to access relational databases from XQuery using SQL. With this module, you can execute query, update and prepared statements, and the result sets are returned as sequences of XML elements representing tuples. Each element has children representing the columns returned by the SQL statement. This module uses JDBC to connect to a SQL server. Hence, your JDBC driver will need to be added to the classpath, too. If you work with the full distributions of BaseX, you can copy the driver into the {{Code|lib}} directory. To connect to MySQL, for example, download the [https://dev.mysql.com/downloads/connector/j/ Connector/J Driver] and extract the archive into this directory. =Conventions= {{Mark|Updated with Version 9.0}}: All functions and errors in this module are assigned to the <code><nowiki>http://basex.org/modules/sql</nowiki></code> namespace, which is statically bound to the {{Code|sql}} prefix.<br/> =FunctionsEvaluation=

==sqlxquery:initeval==

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|{{Func|sqlxquery:initeval|$class query as xs:stringanyAtomicType|empty-sequenceitem()*}}<br />{{Func|xquery:eval|$query as xs:anyAtomicType, $bindings as map(*)?|item()*}}<br />{{Func|xquery:eval|$query as xs:anyAtomicType, $bindings as map(*)?, $options as map(*)?|item()*}}<br />|-valign="top"

|This function initializes Evaluates the supplied {{Code|$query}} and returns the resulting items. If the query is of type {{Code|xs:anyURI}}, the module located at this URI will be retrieved (a relative URI will be resolved against the static base URI). Otherwise, the input is expected to be of type {{Code|xs:string}}.Variables and context items can be declared via {{Code|$bindings}}. The specified keys must be QNames or strings:* If a key is a QName, it will be directly adopted as variable name.* It a key is a string, it may be prefixed with a JDBC driver dollar sign. Namespace can be specified via using the [http://www.jclark.com/xml/xmlns.htm Clark Notation].* If the specified string is empty, the value will be bound to the context item.The {{Code|$classoptions}} parameter contains evaluation options:* {{Code|permission}}: the query will be evaluated with the specified permissions (see [[User Management]]). This step might * {{Code|timeout}}: query execution will be interrupted after the specified number of seconds.* {{Code|memory}}: query execution will be superfluous interrupted if the SQL database specified number of megabytes will be exceeded. This check works best if only one process is not embeddedrunning at the same time.<brMoreover, please note that this option enforces garbage collection, so it will take some additional time, and it requires GC to be enabled in your JVM.* {{Code|base-uri}}: set [https://www.w3.org/ >TR/xquery-31/#dt-static-base-uri base-uri property] for the query. Overwrites the base URI of the query; will be used when resolving relative URIs by functions such as {{Code|fn:doc}}.* {{Code|pass}}: passes on the original error info (line and column number, optional file uri). By default, this option is {{Code|false}}.|-valign="top"

|{{Error|initupdate|XQuery Errors#SQL Functions Errors}} the specified driver is not foundquery contains [[XQuery Update#Updating Expressions|updating expressions]].|} ==sql:connect== {| width='100%'|-| width='120' | '''Signatures'''|{{Func|sql:connect|$url as xs:string|xs:anyURI}}<br/ >{{FuncError|sql:connectpermission|$url as xs:string, $user as xs:string, $password as xs:string|xs:anyURI#Errors}}insufficient permissions for evaluating the query.<br/ >{{FuncError|sql:connecttimeout|$url as xs:string, $user as xs:string, $password as xs:string, $options as map(*)|xs:anyURI#Errors}}query execution exceeded timeout.<br/ >|-| '''Summary'''|This function establishes a connection to a relational database and returns a connection id. The parameter {{CodeError|limit|$url#Errors}} is the URL of the database and shall be of the form: {{Code|jdbc:query execution exceeded memory limit.<driver name>:[//<server>[br/<database>]]}}. If the parameters {{Code|$user}} and {{Code|$password}} are specified, they are used as credentials for connecting to the database. The {{Code|$options}} parameter can be used to set connection options.|-| '''Errors'''|{{Error|errornested|XQuery Errors#SQL Functions Errors}} an SQL exception occurs, enested query evaluation is not allowed.g. missing JDBC driver or not existing relation<br/>Any other error that may occur while evaluating the query.|-valign="top"

|Connects to an SQL Server and sets autocommit to * {{Code|true}}xquery:<pre class=eval("brush:xquery1+3">sql:connect('dbc:sqlserver://DBServer', map { 'autocommit': true() })</pre>|} ==sql:execute== {{Mark|Updated with Version 9.0}}: Return update count for updating statements. returns {{Code|$options4}} argument added. {| width='100%'|-| width='120' | '''Signatures'''|{{Func|sql:execute|$id as xs:anyURI, $statement as xs:string|item()*}}<br/>{{Func|sql:execute|$id as xs:anyURI, $statement as xs:string, $options as map(*)|item()*}}|-| '''Summary'''| This function executes an SQL {{Code|$statement}}If a URI is supplied, using the connection with query in the specified {{Code|$id}}. The returned result depends on the kind of statement:* If an update statement was executed, the number of updated rows file will be returned as integer.* Otherwise, an XML representation of all results will be returned.With {{Code|$options}}, the following parameter can be setevaluated:* {{Code|timeout}}: query execution will be interrupted after the specified number of seconds.|-| '''Errors'''|{{Error|error|XQuery Errors#SQL Functions Errors}} an SQL exception occurs, e.g. not existing relation is retrieved.<br/ >{{Error|id|XQuery Errors#SQL Functions Errors}} the specified connection does not exist.<br/ syntaxhighlight lang="xquery">|} ==sqlxquery:execute-prepared== {{Mark|Updated with Version 9.0}}: Return update count for updating statements. {| width='100%'|-| width='120' | '''Signatures'''|{{Func|sql:execute-prepared|$id as eval(xs:anyURI, $params as element(sql:parameters'cleanup.xq')|item()*}}<br/syntaxhighlight>{{Func|sql:execute-prepared|$id as xs:anyURI, $params as element(sql:parameters), $options as map(*)|item()*}}|-| '''Summary'''| This function executes a prepared statement with You can bind the specified {{Code|$id}}context and e. The output format is identical to [[#sql:execute|sql:execute]]g. The optional parameter {{Code|$params}} is an element {{Code|<sql:parameters/>}} representing the parameters for operate on a prepared statement along with their types and values. The following schema shall be usedcertain database only:<br/ ><pre classsyntaxhighlight lang="brush:xquery">element sqlxquery:parameters { element sql:parameter { attribute type { eval("int" | "string" | "boolean" | "date" | "double" | "float" | "short" | "time" | "timestamp" | "sqlxml//country" }, attribute null map { "true" | "false" '': db:get('factbook') }?, text }+}?)</presyntaxhighlight>With {{Code|$options}}, the * The following parameter can be set:* {{Code|timeout}}: query execution will be interrupted after the specified number expressions use strings as keys. All of seconds.|-| '''Errors'them return 'XML'|{{Error|attribute|XQuery Errors#SQL Functions Errors}} an attribute different from {{Code|type}} and {{Code|null}} is set for a {{Code|<sql:parameter/>}} element.<br/ >{{Error|error|XQuery Errors#SQL Functions Errors}} an SQL exception occurs, e.g. not existing relation is retrieved.<br/ syntaxhighlight lang="xquery">{{Error|id|XQuery Errors#SQL Functions Errors}} the specified connection does not existxquery:eval(".<br/ >{{Error|parameters|XQuery Errors#SQL Functions Errors}} wrong number of {{Code|<sql:parameter/>}} elements", or parameter type is not specified.<br/>{{Error|type|XQuery Errors#SQL Functions Errors}} the value of a parameter cannot be converted to the specified format.|} ==sql:prepare== map {| width='100%'|-| width='120' | '''Signatures'''|{{Func|sql:prepare|$id as xs:anyURI, $statement as xs:string|xs:anyURI}}|-| 'XML''Summary'''|This function prepares an SQL {{Code|$statement}}), using the specified connection {{Code|$id}}, and returns the id reference to this statement. The statement is a string with one or more '?' placeholders. If the value of a field has to be set to {{Code|NULL}}, then the attribute {{Code|null}} of the {{Code|<sql:parameter/>}} element must be {{Code|true}}.|-| '''Errors'''|{{Error|error|XQuery Errors#SQL Functions Errors}} an SQL exception occurs.<br/ >{{Error|id|XQuery Errors#SQL Functions Errors}} the specified connection does not exist.<br/ >|}

==sqlxquery:commit==eval("declare variable $xml external; $xml", map { 'xml': 'XML' }),

{| width='100%'|-| width='120' | '''Signatures'''|{{Func|sql:commit|$id as xsxquery:anyURI|empty-sequenceeval()}}|-| '''Summary' "declare namespace pref='URI';| This function commits the changes made to a relational database, using the specified connection {{Code| declare variable $id}}.|-| '''Errors'''|{{Error|error|XQuery Errors#SQL Functions Errors}} an SQL exception occurs.<br/ >{{Error|id|XQuery Errors#SQL Functions Errors}} the specified connection does not exist.<br/ >|} ==sqlpref:rollback== {| width='100%'|-| width='120' | '''Signatures'''xml external;|{{Func|sql:rollback| $id as xspref:anyURI|empty-sequence()}}|-| '''Summary'''| This function rolls back the changes made to a relational databasexml", using the specified connection {{Code|$id}}.|-| '''Errors'''|{{Error|error|XQuery Errors#SQL Functions Errors}} an SQL exception occurs.<br/ >{{Error|id|XQuery Errors#SQL Functions Errors}} the specified connection does not exist.<br/ >|} ==sql:close== {| width='100%'|-| width='120' | '''Signatures'''|{{Func|sql:close|$id as xs:anyURI|empty-sequence()}}|-| '''Summary'''| This function closes a database connection with the specified { map {Code|$id}}.<br/>Opened connections will automatically be closed after the XQuery expression has been evaluated, but in order to save memory, it is always recommendable to close connections that are not used anymore.|-| '''Errors'''|{{Error|error|XQuery Errors#SQL Functions Errors}} an SQL exception occurs.<br/ >{{Error|id|XQuery Errors#SQL Functions Errors}} the specified connection does not exist.<br/ >|URI} =Examples= ==Direct queries== A simple select statement can be executed as follows: <pre class="brush:xquery">let $id := sql:connect("jdbc:postgresql://localhost:5432/coffeehouse")return sql:execute($id, "SELECT * FROM coffees WHERE price < 10")</pre> The result may look like: <pre class="brush:xml"><sql:row xmlns:sql="http://basex.org/modules/sql"> <sql:column name="cof_name">French_Roast</sql:column> <sql:column name="sup_id">49</sql:column> <sql:column name="price">9.5</sql:column> <sql:column name="sales">15</sql:column> <sql:column name="total">30</sql:column></sql:row><sql:row xmlns:sql="http://basex.org/modules/sql"> <sql:column name="cof_name">French_Roast_Decaf</sql:column> <sql:column name="sup_id">49</sql:column> <sql:column name="price">7.5</sql:column> <sql:column name="sales">10</sql:column> <sql:column name="total">14</sql:column></sql:row></pre> ==Prepared Statements== A prepared select statement can be executed in the following way: <pre class="brush:xquery">(: Establish a connection :)let $conn := sql:connect("jdbc:postgresql://localhost:5432/coffeehouse")(: Obtain a handle to a prepared statement :)let $prep := sql:prepare($conn, "SELECT * FROM coffees WHERE price < ? AND cof_name = ?")(: Values and types of prepared statement parameters :)let $params := <sql:parameters> <sql:parameter type='double'>10</sql:parameter> <sql:parameter type='stringXML'>French_Roast</sql:parameter> </sql:parameters>(: Execute prepared statement :)return sql:execute-prepared($prep, $params)</pre> ==SQLite== The following expression demonstrates how SQLite can be addressed using the [http://bitbucket.org/xerial/sqlite-jdbc Xerial SQLite JDBC driver]: <pre class="brush:xquery">(: Initialize driver :)sql:init("org.sqlite.JDBC"),(: Establish a connection :)let $conn := sql:connect("jdbc:sqlite:database.db")return ( (: Create a new table :) sql:execute($conn, "drop table if exists person"), sql:execute($conn, "create table person (id integer, name string)"), (: Run 10 updates :) for $i in 1 to 10 let $q := "insert into person values(" || $i || ", '" || $i || "')" return sql:execute($conn, $q), (: Return table contents :) sql:execute($conn, "select * from person")}

</presyntaxhighlight>* The following expressions use QNames as keys. All of them return 'XML':<br/><syntaxhighlight lang=Errors"xquery">declare namespace pref ='URI';

xquery:eval("declare variable $xml external; $xml", map {{Mark|Updated with Version 9.0xs:QName('xml'): 'XML' }}:),

{| classlet $query :="wikitable" widthdeclare namespace pref="100%"'URI';! width="110"|Code|Description|-|{{Code|attribute}}|An attribute different from {{Code|type}} and {{Code|null}} is set for a {{Code|&lt;sql declare variable $pref:parameter/&gtxml external;}} element.|- $pref:xml"|let $vars := map {{Code|error}}|An SQL exception occurred.|-|{{Code|id}xs:QName('pref:xml'): 'XML' }|A connection does not exist.|-|{{Code|init}}|A database driver is not found.|-|{{Code|parameters}}|Wrong number of {{Code|&lt;sqlreturn xquery:parameter/&gt;}} elementseval($query, or parameter type is not specified.$vars)|-|{{Code|type}}|The value of a parameter cannot be converted to the specified format.</syntaxhighlight>

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|{{Func|xquery:eval-update|$query as xs:stringanyAtomicType|item()*}}<br />{{Func|xquery:eval-update|$query as xs:stringanyAtomicType, $bindings as map(*)?|item()*}}<br />{{Func|xquery:eval-update|$query as xs:stringanyAtomicType, $bindings as map(*)?, $options as map(xs:string, xs:string*)?|item()*}}<br />|-valign="top"

|Evaluates {{Code|$a query}} as updating XQuery expression at runtime.<br/>All updates will be added to the [[XQuery Update#Pending Update List|Pending Update List]] of the main query and performed after the evaluation of the main query.<br />The rules of the {{Code|$bindings}} and {{Code|$options}} parameters for all arguments are the same as for [[#xquery:eval{{Function||xquery:eval]]}}.|-valign="top"

=Parsing=xquery:invoke== {| width='100%'|-| width='120' | '''Signatures'''|{{Func|xquery:invoke|$uri as xs:string|item()*}}<br />{{Func|xquery:invoke|$uri as xs:string, $bindings as map(*)?|item()*}}<br />{{Func|xquery:invoke|$uri as xs:string, $bindings as map(*)?, $options as map(*)|item()*}}<br />|-| '''Summary'''|Evaluates the XQuery module located at {{Code|$uri}} at runtime and returns the resulting items. A relative URI will be resolved against the static base URI of the query.<br />The rules of the {{Code|$bindings}} and {{Code|$options}} parameters are the same as for [[#xquery:eval|xquery:eval]].|-| '''Errors'''|{{Error|update|#Errors}} the expression contains [[XQuery Update#Updating Expressions|updating expressions]].<br/>{{Error|permission|#Errors}} insufficient permissions for evaluating the query.<br/>{{Error|BXXQ0004|#Errors}} query execution exceeded timeout.<br/>{{Error|nested|#Errors}} nested query evaluation is not allowed.<br/>Any other error that may occur while evaluating the query.|} ==xquery:invoke-update== {| width='100%'|-| width='120' | '''Signatures'''|{{Func|xquery:invoke-update|$uri as xs:string|item()*}}<br />{{Func|xquery:invoke-update|$uri as xs:string, $bindings as map(*)?|item()*}}<br />{{Func|xquery:invoke-update|$uri as xs:string, $bindings as map(*)?, $options as map(*)|item()*}}<br />|-| '''Summary'''|Evaluates the updating XQuery module located at {{Code|$uri}} at runtime. A relative URI will be resolved against the static base URI of the query.<br />The rules of the {{Code|$bindings}} and {{Code|$options}} parameters are the same as for [[#xquery:eval|xquery:eval]].|-| '''Errors'''|{{Error|update|#Errors}} the expression contains no [[XQuery Update#Updating Expressions|updating expressions]].<br/>{{Error|permission|#Errors}} insufficient permissions for evaluating the query.<br/>{{Error|BXXQ0004|#Errors}} query execution exceeded timeout.<br/>{{Error|nested|#Errors}} nested query evaluation is not allowed.<br/>Any other error that may occur while evaluating the query.|}

{{MarkAnnounce|Updated with Version 9.010:}} {{Code|$query}}: can additionally be of type {{codeCode|base-urixs:anyURI}} option added.

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|{{Func|xquery:parse|$query as xs:stringanyAtomicType|item()?}}<br />{{Func|xquery:parse|$query as xs:stringanyAtomicType, $options as map(*)?|item()?}}<br />|-valign="top"

|Parses the specified {{Code|$query}} string as XQuery module and returns the resulting query plan. If the query is of type {{Code|xs:anyURI}}, the module located at this URI will be retrieved (a relative URI will be resolved against the static base URI). Otherwise, the input is expected to be of type {{Code|xs:string}}. The {{Code|$options}} parameter influences the output:

* {{Code|pass}}: passes on by default, the original option is {{Code|false}}. If an error info (is raised, the line and /column number, and the optional file uri)will refer to the location of the function call. By default, this  If the option is {{Code|false}}enabled, the line/column and file uri will be adopted from the raised error.

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<pre classsyntaxhighlight lang='brush:"xml'">

</presyntaxhighlight>|} ==xquery:parse-uri== {{Mark|Updated with Version 9.0}}: {{code|base-uri}} option added. {| width='100%'|-| width='120' | '''Signatures'''|{{Func|xquery:parse-uri|$uri as xs:string|item()?}}<br />{{Func|xquery:parse-uri|$uri as xs:string, $options as map(*)|item()?}}<br />|-| '''Summary'''|Parses the XQuery module located at {{Code|$uri}} and returns the resulting query plan. A relative URI will be resolved against the static base URI of the query. The rules for the {{Code|$options}} parameter are the same as for [[#xquery:parse|xquery:parse]].|-| '''Errors'''|Any error that may occur while parsing the query.

Parallel query execution is recommendable if you have various calls that require a lot of time, but that cannot be sped up by rewriting the code. This is e. g. the case if external URLs are called. If you are parallelizing local data reads (such as the access to a database), single-threaded queries will usually be faster, because parallelized access to disk data often results in randomized access patterns, which can hardly will rarely be optimized by the caching strategies of HDHDDs, SSDs, SSD or the operating system.

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<pre classsyntaxhighlight lang='brush:"xquery'">

</presyntaxhighlight>

<pre classsyntaxhighlight lang='brush:"xquery'">let $funcs xquery:=fork-join(

let $url := 'http://url.com/path/' || $segment

return xquery:fork-join($funcs)</presyntaxhighlight>|-valign="top"

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* Added: [[#xquery:invoke-uri{{Function||xquery:invoke-uri]]update}}* Updated: [[#xquery:eval{{Function||xquery:eval]]}}: {{Code|pass}} option added* Updated: [[#xquery:parse{{Function||xquery:parse]]}}, [[#xquery:parse-uri{{Function||xquery:parse-uri]]}}: {{Code|base-uri}} option added* Updated: xquery:update renamed to [[#xquery:eval-update{{Function||xquery:eval-update]]}}

* Added: [[#xquery:fork-join{{Function||xquery:fork-join]]}}* Updated: [[#xquery:eval{{Function||xquery:eval]]}}: {{Code|base-uri}} option added

* Deleted: xquery:type (moved to [[Profiling Module]])

* Added: [[#xquery:parse-uri{{Function||xquery:parse-uri]]}}* Updated: [[#xquery:parse{{Function||xquery:parse]]}}: {{Code|pass}} option added

* Added: xquery:update, [[#xquery:parse{{Function||xquery:parse]]}}* Deleted: [[#xquery:evaluate|xquery:evaluate]] (opened databases will now be closed by main query)

* Added: [[#xquery:evaluate{{Function||xquery:evaluate]]}}