XQuery

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XQuery
Source http//www.srdc.metu.edu.tr/webpage/cours
es/ceng520
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What is XQuery?
A language for querying XML A human-readable
syntax for an XML query language A functional
programming language The product of the W3Cs
XML Query Working Group
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History
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Resources
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XQuery 1.0 XPath 2.0
XQueryX 1.0
XQuery 1.0
XPath 2.0
XQuery 1.0 Xpath 2.0Formal Semantics
XQuery 1.0 Xpath 2.0Functions Operators
XQuery 1.0 Xpath 2.0Data Model
XQuery 1.0 Xpath 2.0Requirements Use Cases
XML Schema 1.0
XML 1.0
Namespaces 1.0
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Does the world need a new query language?
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Nesting
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Metadata
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Ordering
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Missing Information
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General XQuery Rules
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XQuery Expressions
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Functions
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Path Expressions
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Predicates
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Expressions
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Logical Expressions
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Constructors
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FLWOR Expressions
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An Example Query
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Ways of qualifying a node ("Kind tests")
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Testing Types
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Structure of an XQuery
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Namespace Declarations
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Schema Imports
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Function Definitions
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Modules
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Modules (continued)
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Two Phases in Query Processing
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Summary and Prognosis
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Some Examples(1)
FOR - LET - WHERE - RETURN Similar to SQLs
SELECT - FROM - WHERE for book in
document("http//www.bn.com/bib.xml")//book
where book/publisher "Addison-Wesley" return
ltbookgt book/title,
book/author lt/bookgt
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Some Examples(2)
_at_ indicates, attribute for bk in
document("http//www.bn.com/bib.xml")/bib/book
where bk/_at_year lt "1997 return bk/title
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Some Examples(3)
Nested fors can be used, for a in
document("http//www.bn.com/bib.xml") for b
in a/bib for c in b/book
return ltauthorlistgt c/author lt/authorlistgt
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Some Examples(4)
More than one bindings b, t, a ltresultsgt
for b in document("http//www.bn.com/bib.xml")/bi
b/book, t in b/title, a in b/author
return ltresultgt t a
lt/resultgt lt/resultsgt
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Some Examples(5)
Join operation between two XML files ltbooks-with-
pricesgt for b in document("http//www.bn.com
/bib.xml")//book, a in document("http//www
.amazon.com/reviews.xml")//entry where
b/title a/title return
ltbook-with-pricesgt b/title
ltprice-amazongt a/price/text() lt/price-amazongt
ltprice-bngt b/price/text() lt/price-bngt
lt/book-with-pricesgt lt/books-with-pricesgt
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Some Examples(6)
SORTBY can be used, ltbibliographygt FOR
book IN document("bib.xml")//book RETURN
ltbookgt book/author,
book/title lt/bookgt SORTBY
(author, title) lt/bibliographygt
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Some Examples(7)
A function example FUNCTION depth(ELEMENT e)
RETURNS integer -- An empty element has
depth 1 -- Otherwise, add 1 to max depth of
children IF empty(e/) THEN 1
ELSE max(depth(e/)) 1 depth(document("partl
ist.xml"))
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Some Examples(8)
min(), max(), count(), avg(), sum() ltresultsgt L
ET doc document("prices.xml")/prices/book RETU
RN ltcount-of-pricegt count(doc/price)
lt/count-of-pricegt ltavgpricegt
avg(doc/price) lt/avgpricegt ltmaxpricegt
max(doc/price) lt/maxpricegt ltminpricegt
min(doc/price) lt/minpricegt ltsumpricegt
sum(doc/price) lt/sumpricegt lt/resultsgt
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Some Examples(9)
Another example FOR item IN document("news_item
.xml")//news_item WHERE contains(
string(item/content), "Gorilla Corporation"
) RETURN ltitem_summarygt
item/title/text() ".
item/date/text() ". string(
(item//par)1 ) lt/item_summary
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Some Examples(10)
Insert, Replace, Delete FOR e IN /empINSERT
ltn_skillsgt count(e/skill) lt/n_skillsgt BEFORE
e/skill1 FOR e IN /empWHERE e/empno
"1234REPLACE e/job WITH ltjobgt "Broom Tester"
lt/jobgt FOR e IN /emp/job "Programmer",
s IN e/skillWHERE s/rating lt 4 OR
s/cert_date lt date("1995-01-01")DELETE s
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Thank you for your attention