XQuery 3.0
This article summarizes the most important features of the upcoming Version 3.0 of the XQuery language that have already been implemented in BaseX.
Group By
FLWOR expressions have been extended by the group by clause, which is well-established among relational database systems. Group by clauses can be used to group query results based on its values.
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Try/Catch
The try/catch construct can be used to handle errors at runtime:
Example:
try {
1 + '2'
} catch *($code, $desc) {
concat('Error [', $code, ']: ', $desc)
}
Result: Error [XPTY0004]: '+' operator: number expected, string found.
Switch
The switch statement is available in many other programming languages. It chooses one of several expressions to evaluate based on its input value.
Example:
for $fruit in ("Apple", "Pear", "Peach")
return switch ($fruit)
case "Apple" return "red"
case "Pear" return "green"
case "Peach" return "pink"
default return "unknown"
Result: red green pink
Serialization
Serialization parameters can now be defined within XQuery expressions. All available parameters are supported, which are specified in the W3C Serialization Document. Parameters are placed in the query prolog and need to be specified as option declarations, using the output prefix.
Example:
declare option output:omit-xml-declaration "no"; declare option output:method "xhtml"; <html/>
Result: <?xml version="1.0" encoding="UTF-8"?><html></html>
Functions
This paragraph lists all new functions of the XQuery 3.0 Specification that are already supported in BaseX.
The following functions have been added:
math:pi(),math:sin(), and many others (see Math Functions)fn:head()fn:tail()fn:generate-id()fn:analyze-string()fn:environment-variable()fn:available-environment-variables()fn:unparsed-text-available()fn:unparsed-text-lines()fn:unparsed-text()fn:element-with-id()fn:parse-xml()fn:uri-collection()fn:serialize()
The following functions have a different signature:
fn:document-uri()with 0 argumentsfn:string-join()with 1 argumentfn:node-name()with 0 argumentsfn:round()with 2 argumentsfn:data()with 0 arguments
The following functions are partially supported:
fn:format-integer()fn:format-number()fn:format-dateTime()fn:format-date()fn:format-time()
