29 pages

English

Xquery Tutorial

Showyeg - Knoblock

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29 pages

English

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Xquery TutorialCraig KnoblockUniversity of Southern California„„„„„„„„„„ReferencesXQuery 1.0: An XML Query Language www.w3.org/TR/xquery/XML Query Use Cases www.w3.org/TR/xmlquery-use-casesXquery Interpreter:http://prometheus2.isi.edu:9001/xquery.htmlAdvice: Case mattersWrite your queries incrementally!It is hard to debug entire queriesExample XML Document: bib.xml TCP/IP Illustrated StevensW. Addison-Wesley 65.95 Advanced Programming in the Unix environment 65.95 Example XML Document: bib.xml Data on the Web AbiteboulSergeBunemanPeterSuciuDan Morgan Kaufmann Publishers 39.95 The Economics of Technology and Content for Digital TV GerbargDarcy CITI Kluwer Academic Publishers 129.95 „„„„„„Xquery OverviewXquery is an expression languageEvery statement evaluates to some resultlet $x := 5 let $y := 6 return 10*$x+$yEvaluates to 56Primitive typesNumber, boolean, ...

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Publié par	Showyeg
Nombre de lectures	17
Langue	English

Extrait

Xquery

Tutorial

Craig Knoblock

University of Southern California

References

XQuery 1.0: An XML Query Language ro/gRTx/wwww..3query/ XML Query Use Cases www.w3.org/TR/xmlquery-use-cases Xquery Interpreter: uexq.hryltmuehtemorp//:ptth1/00:9du.esi.is2 Advice: Case matters Write your queries incrementally! It is hard to debug entire queries

Example XML Document: bib.xml

<bib> <book year="1994"> <title>TCP/IP Illustrated</title> <author><last>Stevens</last><first>W.</first></author> <publisher>Addison-Wesley</publisher> <price> 65.95</price> </book> <book year="1992"> <title>Advanced Programming in the Unix environment</title> <author><last>Stevens</last><first>W.</first></author> <publisher>Addison-Wesley</publisher> <price>65.95</price> </book>

utho></airstr</fsa>t>rl<tuoh>ra<ir<ft>as/lu<ciSu/<>tsrif/<naD>ts</first>st>Serge<>uahtro/<uahtroemun</anla><>Bst>tsretePtsalif<>9.<5 >93ec >p/irok> </bok ye<boo9991"=raltit< >"Ece The>s icomonuahtro >p<builhser>Morgan KaufmaP nnilburehsp/<sliubersh<p> cerisrif/<ycraD>tsri<ft>as/lg<arrbGetaoiifil/<faICITion>liataffit> <of tiD roC dnetnogolany Tofhnec >l<sa>t< detiro</title>gital TVoo/b <e>ib/b <k>.921>ecicirp/<59 >

Example XML Document: bib.xml

shli>KerwelucarA< >nide/>rotbup<</publisher> <predim cuPlbsiehsr"> <2000ar="k yeb<ooast><fireboul</lsa>tbAtituoh>rl<leit<a> Wee /tb<o atht nltitaD>e

Xquery Overview

Xquery is an expression language

Every statement evaluates to some result := 5 let $y := 6 return 10*$x+$ylet $x Evaluates to 56

Primitive types

Number, boolean, strings, dates, times, durations, and XML types

Nodes and Expressions

Various functions create or return nodes Document function reads an XML file .wsi.idett:p//wwdoc("h-ofni/u agents/courses/iiweb/bib.xml") We will use doc(“bib.xml”) throughout, but you must use the expansion to run the demo Element constructor creates a node: <doc><par>Blah Blah</par></doc> Use curly braces to embed Xquery expressions inside an element constructor

Path Expressions

Xquery uses path expressions from Xpath (a W3C standard) Let $b :=doc("bib.xml")

return <result>{$b/bib/book}</result>

/book selects the child elements named book

/book/author selects the author elements of the top-level book elements

Path Expressions (cont.)

//book returns all book elements that appear anywhere in the document //book[author/last = Stevens] all book elements with author = Hunter //book[@year > 1999] book elements with attribute year > 1999 //book[@pages] all book elements that have a pages attribute

Advanced Path Expressions

//book/(author | editor)  returns all author or editor elements from current node

(//book | //collection)[publisher = $pub]  books for collections where publisher equals $pub variable

(//book)[1]/title/text()  returns the text nodes of the first book element

FLWOR Expressions

For/Let, Where, Order by, Result Expressions

<html>{

let $d := doc(bib.xml")/bib

for $b in $d/book

where $b/@year > 1998

order by $b/publisher

return <book>{$b/title, $b/price, $b/publisher}</book>

}</html>

Projection

Return the names of all authors of books let $d := doc(bib.xml") return <result>{$d/bib/book/author}</result> = <result> <author><last>Stevens</last><first>W.</first></author> <author><last>Stevens</last><first>W.</first></author> <author><last>Abiteboul</last><first>Serge</first></author> <author><last>Buneman</last><first>Peter</first></author> <author><last>Suciu</last><first>Dan</first></author> </result>