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20/1/2009 2
What is XQuery ?
 XQuery is a standardized language that can be used to query
XML documents.
 XQuery is to XML as SQL is to relational databases.
 XQuery queries of XML data are built using XPath
expressions.

<?xml version="1.0" encoding="ISO-8859-1"?>
<bookstore>
<book category="COOKING">
<title lang="en">Everyday Italian</title>
<author>Giada De Laurentiis</author>
<year>2005</year>
<price>30.00</price>
</book>
<book category="CHILDREN">
<title lang="en">Harry Potter</title>
<author>J K. Rowling</author>
<year>2005</year>
</book>
<book category="WEB">
<title lang="en">XQuery Kick Start</title>
<author>James McGovern</author>
<author>Per Bothner</author>
<author>Kurt Cagle</author>
<author>James Linn</author>
<author>Vaidyanathan Nagarajan</author>
<year>2003</year>
</book>
<title lang="en">Learning XML</title>
<author>Erik T. Ray</author>
<year>2003</year>
</book>
</bookstore>

doc("books.xml")
The doc() function is used to open an XML document
doc("books.xml")/bookstore/book/title
doc() function

XPath expressions <?xml version="1.0" encoding="ISO-8859-1"?>
<bookstore>
<year>2005</year>
</book>
<year>2005</year>
</book>
<year>2003</year>
</book>
<year>2003</year>
</book>
</bookstore>
/bookstore/book/title

<bookstore>
<year>2005</year>
</book>
<year>2005</year>
</book>
<year>2003</year>
</book>
<year>2003</year>
</book>
</bookstore>
/bookstore/book[price<30]
<year>2005</year>
</book>
Simple query with predicate

FLWOR
 FLWOR stands for:
 FOR
 LET
 WHERE
 ORDER BY
 RETURN

<bookstore>
<year>2005</year>
</book>
<year>2005</year>
</book>
<year>2003</year>
</book>
<year>2003</year>
</book>
</bookstore>
/bookstore/book[price>30]/title
for $x in /bookstore/book
where $x/price>30
return $x/title
FLWOR example

<bookstore>
<year>2005</year>
</book>
<year>2005</year>
</book>
<year>2003</year>
</book>
<year>2003</year>
</book>
</bookstore>
where $x/price>30
Order by $x/title
return $x/title
order by

<bookstore>
<year>2005</year>
</book>
<year>2005</year>
</book>
<year>2003</year>
</book>
<year>2003</year>
</book>
</bookstore>
<ul>
<li><title lang="en">Everyday Italian</title></li>
<li><title lang="en">Harry Potter</title></li>
<li><title lang="en">Learning XML</title></li>
<li><title lang="en">XQuery Kick Start</title></li>
</ul>
<ul>
{
for $x in /bookstore/book/title
order by $x
return <li>{$x}</li>
}
</ul>
XML output

<bookstore>
<year>2005</year>
</book>
<year>2005</year>
</book>
<year>2003</year>
</book>
<year>2003</year>
</book>
</bookstore>
<ul>
<li>Everyday Italian</li>
<li>Harry Potter</li>
<li>Learning XML</li>
<li>XQuery Kick Start</li>
</ul>
<ul>
{
for $x in /bookstore/book/title
order by $x
return <li>{data($x)}</li>
}
</ul>
data() function

<bookstore>
<year>2005</year>
</book>
<year>2005</year>
</book>
<year>2003</year>
</book>
<year>2003</year>
</book>
</bookstore>
<adult>Everyday Italian</adult>
<child>Harry Potter</child>
<adult>Learning XML</adult>
<adult>XQuery Kick Start</adult>
return if ($x/@category="CHILDREN")
then <child>{data($x/title)}</child>
else <adult>{data($x/title)}</adult>
if-then-else

<test>1</test>
<test>2</test>
<test>3</test>
<test>4</test>
<test>5</test>
for $x in (1 to 5)
return <test>{$x}</test>
<test>1 2 3 4 5</test>
let $x := (1 to 5)
return <test>{$x}</test>
FOR
generates a list of bindings of the
variable to each element
LET
generates a single binding of the
variable to the list of elements
FOR and LET

<bookstore>
<year>2005</year>
</book>
<year>2005</year>
</book>
<year>2003</year>
</book>
<year>2003</year>
</book>
</bookstore>
<book>1. Everyday Italian</book>
<book>2. Harry Potter</book>
<book>3. XQuery Kick Start</book>
<book>4. Learning XML</book>
for $x at $i
in /bookstore/book/title
return <book>{$i}. {data($x)}</book>
The at keyword can be used to
count the iteration
at

<test>x=10 and y=100</test>
for $x in (10,20), $y in (100,200)
return <test>x={$x} and y={$y}</test>
<test>1. x=10 and 1. y=100</test>
<test>1. x=10 and 2. y=200</test>
<test>2. x=20 and 1. y=100</test>
<test>2. x=20 and 2. y=200</test>
for $x at $i in (10,20), $y at $j in (100,200)
return <test>{$i}. x={$x} and {$j}. y={$y}</test>

<bookstore>
<year>2005</year>
</book>
<year>2005</year>
</book>
<year>2003</year>
</book>
<year>2003</year>
</book>
</bookstore>
for $b in //book
where some $p in $b/author satisfies
(contains($p,"in"))
return $b/title
for $b in //book
where every $p in $b/author satisfies
(contains($p,"in"))
return $b/title
some, every, in, satisfies

<bookstore>
<year>2005</year>
</book>
<year>2005</year>
</book>
<year>2003</year>
</book>
<year>2003</year>
</book>
</bookstore>
<s>149.93</s>
let $p := for $b in //book
return number($b/price)
return <s>{sum($p)}</s>
<s>30 29.99 49.99 39.95</s>
let $p := for $b in //book
return number($b/price)
return <s>{$p}</s>
sum

<bookstore>
<year>2005</year>
</book>
<year>2005</year>
</book>
<year>2003</year>
</book>
<year>2003</year>
</book>
</bookstore>
<year>2005</year>
<year>2005</year>
<year>2003</year>
<year>2003</year>
let $p := //book/price
let $y := //book/year
return ($p, $y)
Sequence

<bookstore>
<year>2005</year>
</book>
<year>2005</year>
</book>
<year>2003</year>
</book>
<year>2003</year>
</book>
</bookstore>
<year>2005</year>
<year>2005</year>
<year>2003</year>
<year>2003</year>
//book/(price union year)
//book/(price | title)
union

<bookstore>
<year>2005</year>
</book>
<year>2005</year>
</book>
<year>2003</year>
</book>
<year>2003</year>
</book>
</bookstore>
<year>2005</year>
</book>
let $b := //book
return $b[year = "2005"] intersect
$b[number(price) >= 30]
intersect

<bookstore>
<year>2005</year>
</book>
<year>2005</year>
</book>
<year>2003</year>
</book>
<year>2003</year>
</book>
</bookstore>
<year>2005</year>
<year>2005</year>
<year>2003</year>
<year>2003</year>
//book/(* except author)
except

Functions on Numeric Values
number(arg) Returns the numeric value of the argument
abs(num) Returns the absolute value of the argument
ceiling(num) Returns the smallest integer that is greater than the number argument
floor(num) Returns the largest integer that is not greater than the number argument
round(num) Rounds the number argument to the nearest integer

Functions on Strings - 1
string(arg) Returns the string value of the argument
compare(comp1,comp2) Returns -1 if comp1 is less than comp2, 0 if comp1 is equal to
comp2, or 1 if comp1 is greater than comp2
concat(string,string,...) Returns the concatenation of the strings
string-join((string,string,...),sep) Returns a string created by concatenating the string arguments
and using the sep argument as the separator
substring(string,start,len)
substring(string,start)
Returns the substring from the start position to the specified
length. Index of the first character is 1. If length is omitted it
returns the substring from the start position to the end
string-length(string)
string-length()
Returns the length of the specified string. If there is no string
argument it returns the length of the string value of the current
node
normalize-space(string)
normalize-space()
Removes leading and trailing spaces from the specified string,
and replaces all internal sequences of white space with one
and returns the result. If there is no string argument it does the
same on the current node

Functions on Strings - 2
upper-case(string) Converts the string argument to upper-case
lower-case(string) Converts the string argument to lower-case
contains(string1,string2) Returns true if string1 contains string2, otherwise it returns
false
starts-with(string1,string2) Returns true if string1 starts with string2, otherwise it returns
false
ends-with(string1,string2) Returns true if string1 ends with string2, otherwise it returns
false
substring-before(string1,string2) Returns the start of string1 before string2 occurs in it
substring-after(string1,string2) Returns the remainder of string1 after string2 occurs in it
matches(string,pattern) Returns true if the string argument matches the pattern,
otherwise, it returns false
replace(string,pattern,replace) Returns a string that is created by replacing the given pattern
with the replace argument

Aggregate Functions
count((item,item,...)) Returns the count of nodes
avg((arg,arg,...)) Returns the average of the argument values
max((arg,arg,...)) Returns the argument that is greater than the others
min((arg,arg,...)) Returns the argument that is less than the others
sum(arg,arg,...) Returns the sum of the numeric value of each node in the specified
node-set

 http://www.w3schools.com/xquery
 http://www.w3schools.com/xpath/xpath_functions.asp
 http://www.brics.dk/~amoeller/XML/querying/
 XQuery
 Priscilla Walmsley
 O'Reilly Media, Inc. (2007)
 (ISBN 0596006349)
References

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