Changes

XQuery 3.0 is fully supported by BaseX.

Most clauses of FLWOR expressions can now be specified in an arbitrary order: additional {{Code|let}} and {{Code|for}} clauses can be put after a {{Code|where}} clause, and multiple {{Code|where}}, {{Code|order by}} and {{Code|group by}} statements can be used. This means that many nested loops can now be rewritten to a single FLWOR expression.

More information on window clauses, and all other enhancements, can be found in the [http://www.w3.org/TR/xquery-30/#id-windows specification].

The [http://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:

A map operator is defined to be part of a path expression, which may now mix path and map operators. In contrast to the path operator, the results of the map operator will not be made duplicate-free and returned in document order.

FLWOR expressions have been extended to include the [http://www.w3.org/TR/xquery-30/#id-group-by group by] clause, which is well-established among relational database systems. <code>group by</code> can be used to apply value-based partitioning to query results:

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The [http://www.w3.org/TR/xquery-30/#id-try-catch try/catch] construct can be used to handle errors at runtime:

* {{Code|$err:additional}}: error stack trace

The [http://www.w3.org/TR/xquery-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.

'''Result:''' <code>red red</code>

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 write more modular code.

Function items can also be passed as arguments to and returned as results from functions. These so-called [[Higher-Order Functions]] like <code>fn:map</code> and <code>fn:fold-left</code> are discussed in more depth on their own Wiki page.

A ''QName'' can now be directly prefixed with the letter "Q" and a namespace URI in the [http://www.jclark.com/xml/xmlns.htm Clark Notation].

* <code>"java:java.io.FileOutputStream":new("output")</code>

New namespaces can now be created via so-called 'Computed Namespace Constructors'.

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Two vertical bars <code>||</code> (also named ''pipe characters'') can be used to concatenate strings. This operator is a shortcut for the {{Code|fn:concat()}} function.

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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.

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[[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.

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].

The context item can now be specified in the prolog of an XQuery expression:

'''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.

The annotation ensures that an error will only be thrown if the condition yields true. Without the annotation, the error will always be thrown, because the referenced document is not found.

The following functions have been added in the [http://www.w3.org/TR/xpath-functions-30/ XQuery 3.0 Functions and Operators] Specification: