xquery

XQuery

Raji GHAWI

20/1/2009

220/1/2009

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> <price>29.99</price> </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> <price>49.99</price> </book> <book category="WEB"> <title lang="en">Learning XML</title> <author>Erik T. Ray</author> <year>2003</year> <price>39.95</price> </book></bookstore>

doc("books.xml")

<title lang="en">Everyday Italian</title><title lang="en">Harry Potter</title><title lang="en">XQuery Kick Start</title><title lang="en">Learning XML</title>

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> <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> <price>29.99</price> </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> <price>49.99</price> </book> <book category="WEB"> <title lang="en">Learning XML</title> <author>Erik T. Ray</author> <year>2003</year> <price>39.95</price> </book></bookstore>

/bookstore/book/title

<title lang="en">Everyday Italian</title><title lang="en">Harry Potter</title><title lang="en">XQuery Kick Start</title><title lang="en">Learning XML</title>


/bookstore/book[price<30]

<book category="CHILDREN"> <title lang="en">Harry Potter</title> <author>J K. Rowling</author> <year>2005</year> <price>29.99</price></book>

Simple query with predicate

FLWOR

FLWOR stands for: FOR LET WHERE ORDER BY RETURN


/bookstore/book[price>30]/title

<title lang="en">XQuery Kick Start</title><title lang="en">Learning XML</title>

for $x in /bookstore/bookwhere $x/price>30return $x/title

FLWOR example


<title lang="en">Learning XML</title><title lang="en">XQuery Kick Start</title>

for $x in /bookstore/bookwhere $x/price>30Order by $x/titlereturn $x/title

order by


<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/titleorder by $xreturn <li>{$x}</li>}</ul>

XML output


<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/titleorder by $xreturn <li>{data($x)}</li>}</ul>

data() function


<adult>Everyday Italian</adult><child>Harry Potter</child><adult>Learning XML</adult><adult>XQuery Kick Start</adult>

for $x in /bookstore/bookreturn if ($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>

FORgenerates a list of bindings of the variable to each element

LETgenerates a single binding of the variable to the list of elements

FOR and LET


<book>1. Everyday Italian</book><book>2. Harry Potter</book><book>3. XQuery Kick Start</book><book>4. Learning XML</book>

for $x at $i in /bookstore/book/titlereturn <book>{$i}. {data($x)}</book>

The at keyword can be used to count the iteration

at

<test>x=10 and y=100</test><test>x=10 and y=200</test><test>x=20 and y=100</test><test>x=20 and y=200</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>


<title lang="en">Harry Potter</title><title lang="en">XQuery Kick Start</title>

for $b in //bookwhere some $p in $b/author satisfies(contains($p,"in"))return $b/title

<title lang="en">Harry Potter</title>

for $b in //bookwhere every $p in $b/author satisfies(contains($p,"in"))return $b/title

some, every, in, satisfies


<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


<price>30.00</price><price>29.99</price><price>49.99</price><price>39.95</price><year>2005</year><year>2005</year><year>2003</year><year>2003</year>

let $p := //book/pricelet $y := //book/yearreturn ($p, $y)

Sequence


<year>2005</year><price>30.00</price><year>2005</year><price>29.99</price><year>2003</year><price>49.99</price><year>2003</year><price>39.95</price>

//book/(price union year)

//book/(price | title)

union


<book category="COOKING"> <title lang="en">Everyday Italian</title> <author>Giada De Laurentiis</author> <year>2005</year> <price>30.00</price></book>

let $b := //bookreturn $b[year = "2005"] intersect

$b[number(price) >= 30]

intersect


<title lang="en">Everyday Italian</title><year>2005</year><price>30.00</price><title lang="en">Harry Potter</title><year>2005</year><price>29.99</price><title lang="en">XQuery Kick Start</title><year>2003</year><price>49.99</price><title lang="en">Learning XML</title><year>2003</year><price>39.95</price>

//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

http://www.w3schools.com/xquery

http://www.w3schools.com/xpath/xpath_functions.asp

http://www.brics.dk/~amoeller/XML/querying/

xquery

Technology

x return

return x

harry potterj

learning xmlerik

enxquery kick

xtitle return

bookstorebooktitle return

bprice return