Bureaucrats, editor, reviewer, Administrators
13,554
edits
Changes
Jump to navigation
Jump to search
m
A map operator is defined to be part of a path expression, which may now be mixed of path and map operators. In contrast to the map operator, the results of the map operator will not be made duplicate-free and returned in document order. ==Group Bygroup by==
==Try/Catch==Moreover, a value can be assigned to the grouping variable. This is shown in the following example:
The [http'''XQuery:''' <pre lang='xquery'>let $data := <xml> <person country='USA' name='John'/> <person country='USA' name='Jack'/> <person country='Germany' name='Johann'/> </www.w3.orgxml>for $person in $data/TRpersongroup by $country := $person/xquery-30@countryreturn element persons { attribute country { $country }, for $name in $person/#id-try-catch try@name return element name { data($name) }}</catch] construct can be used to handle errors at runtimepre> '''Result:'''<pre lang="xml"><persons country="USA"> <name>John</name> <name>Jack</name></persons><persons country="Germany"> <name>Johann</name></persons></pre>
'''Example:''' ==count== The {{Code|count}} clause enhances the FLWOR expression with a variable that enumerates the iterated tuples. <pre classlang="brush:'xquery"'>try { for $n in (1 + 'to 10)[. mod 2'= 1]count $creturn <number count="{ $c } catch err:XPTY0004 " number="{$n }"/></pre> ==allowing empty== 'Typing error: ' The {{Code|| $errallowing empty}} provides functionality similar to outer joins in SQL:description} catch * { <pre lang='Error [xquery' || >for $err:code || n allowing empty in ()return ']: empty? ' || empty($err:description}n)
'''Result:''' <code>Typing error: '+' operator: number expected, xs:string found.</code>
The [http://www.w3.org/TR/<pre lang='xquery'>for tumbling window $w in (2, 4, 6, 8, 10, 12, 14) start at $s when true() only end at $e when $e -30$s eq 2return <window>{ $w }</window></#id-switch switch] statement is available in many other programming languages. It chooses one of several expressions to evaluate based on its input value.pre>
'''Example:''' <pre class="brush:xquery">for $fruit in ("Apple"More information on window clauses, "Pear"and all other enhancements, "Peach")return switch ($fruit) case "Apple" return "red" case "Pear" return "green" case "Peach" return "pink" default return "unknown"<can be found in the [https:/pre> '''Result:''' <code>red green pink</code>www.w3.org/TR/xquery-30/#id-windows specification].
==Function Items==
A The [https://www.w3.org/TR/xquery-30/#id-try-catch try/catch] construct can be used to handle errors at runtime: '''Example:''' <pre lang='xquery'>try { 1 + '2'} catch err:XPTY0004 { 'Typing error: ' || $err:description} catch * { 'Error [' || $err:code || ']: ' || $err:description}</pre>'''Result:'''QName<code>Typing error: '+' can now be directly prefixed operator: number expected, xs:string found.</code> Within the scope of the catch clause, a number of variables are implicitly declared, giving information about the error that occurred: * {{Code|$err:code}} error code* {{Code|$err:description}}: error message* {{Code|$err:value}}: value associated with the letter "Q" and a namespace error (optional)* {{Code|$err:module}}: URI in of the module where the error occurred* {{Code|$err:line-number}}: line number where the error occurred* {{Code|$err:column-number}}: column number where the error occurred =Switch= The [httphttps://www.jclarkw3.comorg/xmlTR/xmlnsxquery-30/#id-switch switch] statement is available in many other programming languages. It chooses one of several expressions to evaluate based on its input value.htm Clark Notation] '''Example:''' <pre lang='xquery'>for $fruit in ("Apple", "Pear", "Peach")return switch ($fruit) case "Apple" return "red" case "Pear" return "green" case "Peach" return "pink" default return "unknown"</pre> '''Result:''' <code>red green pink</code> The expression to evaluate can correspond to multiple input values. '''Example:'''<pre lang='xquery'>for $fruit in ("Apple", "Cherry")return switch ($fruit) case "Apple" case "Cherry" return "red" case "Pear" return "green" case "Peach" return "pink" default return "unknown"</pre>'''Result:''' <code>red red</code> =Expanded QNames= A ''QName'' can be prefixed with the letter {{Code|Q}}, the namespace URI wrapped in curly braces and the local name.
The syntax differed in older versions of the XQuery 3.0 specification, in which the prefixed namespace URI was quoted:=Namespace Constructors=
* <code><nowiki>"http://www.w3.org/2005/xpathNew namespaces can be created via so-functions/math":pi()</nowiki></code>* <code>"java:java.iocalled 'Computed Namespace Constructors'.FileOutputStream":new("output")</code>
==Namespace Constructors== New namespaces can now be created via so-called 'Computed Namespace Constructors'. <pre classlang="brush:'xquery"'>
==String Concatenations==
==External Variables==
==Serialization==
<<html/>>
==Context Item==In BaseX, the {{Code|output}} prefix is statically bound and can thus be omitted. Note that all namespaces need to be specified when using external APIs, such as [http://xqj.net/basex/ XQJ].
==Annotations==
==Functions==
BaseX supports all The following functions that have been added in Version 3.0 of the [httphttps://www.w3.org/TR/xpath-functions-3031/ XQuery 3.0 Functions and Operators] Working Draft. The new functions are listed belowSpecification:
* <code>math:pi()</code>, <code>math:sin()</code>, and many others (see [[Math Module]])* <code>fn:analyze-string()</code>* , <code>fn:available-environment-variables()</code>* , <code>fn:element-with-id()</code>* , <code>fn:environment-variable()</code>* , <code>fn:filter()</code>* , <code>fn:fold-left()</code>* , <code>fn:fold-right()</code>* , <code>for-each</code>, <code>for-each-pair</code>, <code>fn:format-date()</code>* , <code>fn:format-dateTime()</code>* , <code>fn:format-integer()</code>* , <code>fn:format-number()</code>* , <code>fn:format-time()</code>* , <code>fn:function-arity()</code>* , <code>fn:function-lookup()</code>* , <code>fn:function-name()</code>* , <code>fn:generate-id()</code>* , <code>fn:has-children()</code>* , <code>fn:head()</code>* , <code>fn:innermost()</code>* , <code>fn:map()outermost</code>* , <code>fn:mapparse-pairs()xml</code>* <code>fn:outermost()</code>* , <code>fn:parse-xml()-fragment</code>* , <code>fn:path()</code>* , <code>fn:serialize()</code>* , <code>fn:tail()</code>* , <code>fn:unparsed-text()</code>* , <code>fn:unparsed-text-available()</code>* , <code>fn:unparsed-text-lines()</code>* , <code>fn:uri-collection()</code>
* <code>fn:document-uri()</code> with 0 arguments* , <code>fn:string-join()</code> with 1 argument* , <code>fn:node-name()</code> with 0 arguments* , <code>fn:round()</code> with 2 arguments* , <code>fn:data()</code> with 0 arguments
Text replacement - "syntaxhighlight" to "pre"
This article is part of the [[XQuery|XQuery Portal]].It summarizes provides a summary of the most important features of the upcoming [httphttps://www.w3.org/TR/xquery-30/ XQuery 3.0]and [http://www.w3.org/TR/xpath-30/ XPath 3.0] Recommendationsthat have already been implemented in BaseXRecommendation.
==Simple Map Operator=Enhanced FLWOR Expressions=
Most clauses of FLWOR expressions can be specified in an arbitrary order: additional {{MarkCode|Introduced with Version 7.3:let}} The [http://www.w3.org/TR/xquery-30/#id-map-operator simple map] operator and {{Code|!for}} provides clauses can be put after a compact notation for applying the results of a first to a second expression: the resulting items of the first expression are bound to the context item one {{Code|where}} clause, and multiple {{Code|where}}, {{Code|order by one, }} and the second expression is evaluated for each item{{Code|group by}} statements can be used. The map operator may This means that many nested loops can now be used as replacement for rewritten to a single FLWOR expressions:expression.
'''Example:'''
<pre classlang="brush:'xquery"'>(for $country in db: Simple map notation :)get(1 to 10'factbook') ! element node { . },//country(: FLWOR notation :)where $country/@population > 100000000for $i city in $country//city[population > 1000000]group by $name := $country/name[1 to 10]count $idreturn element node <country id='{ $i id }' name='{ $name }'>{ $city/name }</country>
</pre>
FLWOR expressions have been extended to include the [httphttps://www.w3.org/TR/xquery-30/#id-group-by group by] clause, which is well-established among relational database systemsin SQL. <code>group by</code> can be used to apply value-based partitioning to query results:
'''ExampleXQuery:''' <pre classlang="brush:'xquery"'>
for $ppl in doc('xmark')//people/person
let $ic := $ppl/profile/@income
let $income := if($ic < 30000) then "challenge" else if($ic >= 30000 and $ic < 100000) then "standard" else if($ic >= 100000) then "preferred" else "na"
group by $income
order by $income
return element { $income } { count($ppl) }
</pre>
This query is a rewrite of [httphttps://www.ins.cwi.nl/projects/xmark/Assets/xmlquery.txt Query #20] contained in the [httphttps://www.insprojects.cwi.nl/projectsxmark/xmark XMark Benchmark Suite] to use <code>group by</code>.
The query partitions the customers based on their income.
'''Result:'''
<pre classlang="brush:xml">
<challenge>4731</challenge>
<na>12677</na>
<preferedpreferred>314</preferedpreferred>
<standard>7778</standard>
</pre>
In contrast to the relational GROUP BY statement, the XQuery counterpartconcatenates the values of all non-grouping variables that belong to a specific group.In the context of our example, all nodes in <code>//people/person</code> that belong to the <code>preferred</code> partition are concatenated in <code class="brush:xquery">$ppl</code> after grouping has finished.You can see this effect by changing the return statement to:
<pre classlang="brush:'xquery"'>
...
return element { $income } { $ppl }
</pre>
'''Result:'''
<pre classlang="brush:xml">
<challenge>
<person id="person0">
</pre>
</pre>
==Switchwindow== Window clauses provide a rich set of variable declarations to process sub-sequences of iterated tuples. An example:
One of the most distinguishing features added in ''XQuery 3.0'' are ''function items'', also known as ''lambdas'' or ''lambda functions''. They make it possible to abstract over functions and thus writing write more modular code.
'''Examples:'''
<ul>
<li>Declaring a new ''inline function'':
<pre classlang="brush:'xquery"'>let $f := function($x, $y) { $x + $y }
return $f(17, 25)</pre>
'''Result:''' <code>42</code>
</li>
<li>Getting the function item of an existing (built-in oder or user-defined) XQuery function. The arity (number of arguments) has to be specified as there can be more than one function with the same name:<pre classlang="brush:'xquery"'>let $f := math:pow#2
return $f(5, 2)</pre>
'''Result:''' <code>25</code>
</li>
<li>''Partially applying'' another function or function item. This is done by supplying only some of the required arguments, writing the placeholder <code>?</code> in the positions of the arguments left out. The produced function item has one argument for every placeholder.
<pre classlang="brush:'xquery"'>let $f := fn:substring(?, 1, 3)
return (
$f('foo123'),
</ul>
Function items can also be passed as arguments to and returned as results from functions. These so-called [[Higher-Order Functions]] like <code>fn:mapfor-each</code> and <code>fn:fold-left</code> are discussed in more depth on their own Wiki page. =Simple Map Operator= The [https://www.w3.org/TR/xquery-30/#id-map-operator simple map] operator {{Code|!}} provides a compact notation for applying the results of a first to a second expression: the resulting items of the first expression are bound to the context item one by one, and the second expression is evaluated for each item. The map operator may be used as replacement for FLWOR expressions: '''Example:''' <pre lang='xquery'>(: Simple map notation :)(1 to 10) ! element node { . },(: FLWOR notation :)for $i in 1 to 10return element node { $i }</pre> In contrast to path expressions, the results of the map operator will not be made duplicate-free and returned in document order.
==Expanded QNames=Try/Catch=
'''Examples:'''
* <code>Q{java:java.io.FileOutputStream}new("output.txt")</code> creates a new Java file output stream
element node { namespace pref { 'http://url.org/' } }
</pre>
Two vertical bars <code>||</code> (also names named ''pipe characters'') can be used to concatenate strings. This operator is a shortcut for the {{Code|ft:containsconcat()}} function.
<pre classlang="brush:'xquery"'>
'Hello' || ' ' || 'Universe'
</pre>
Default values can now be attached to external variable declarations. This way, an expression can also be evaluated if its external variables have not been bound to a new value.
<pre classlang="brush:'xquery"'>
declare variable $user external := "admin";
"User:", $user
</pre>
[[Serialization|Serialization ]]parameters can now be defined within XQuery expressions. Parameters are placed in the query prolog and need to be specified as option declarations, using the <code>output</code> prefix.
'''Example:'''
<pre classlang='xquery'>declare namespace output ="brushhttp://www.w3.org/2010/xslt-xquery-serialization">;
declare option output:omit-xml-declaration "no";
declare option output:method "xhtml";
</pre>
'''Result:''' <code><?xml version="1.0" encoding="UTF-8"?><html></html></code>
=Context Item= The context item can now be specified in the prolog of an XQuery expressionsexpression:
'''Example:'''
<pre classlang="brush:'xquery"'>
declare context item := document {
<xml>
'''Result:''' <code>5 5</code>
XQuery 3.0 introduces annotations to declare properties associated with functions and variables. For instance, a function may be declared %public, %private, or %updating.
'''Example:'''
<pre classlang="brush:'xquery"'>
declare %private function local:max($x1, $x2) {
if($x1 > $x2) then $x1 else $x2
</pre>
New signatures have been added for the following functions:
=Changelog=
;Version 7.7
* Added: [[#Enhanced FLWOR Expressions|Enhanced FLWOR Expressions]]
;Version 7.3
* Added: [[#Simple map operatorMap Operator|Simple Map Operator]]
;Version 7.2
* Added: [[#Annotations|Annotations]]* Updated: EQName syntax[[#Expanded QNames|Expanded QNames]]
;Version 7.1
* Added: [[#Expanded QNames|Expanded QNames]], Computed [[#Namespace Constructors|Namespace ConstructorConstructors]]
;Version 7.0
* Added: [[#String ConcatenatorConcatenations|String Concatenations]]
[[Category:XQuery]]
