1. Session II Chapter 16 – XQuery http://www.profburnett.com
CMP 051 XML Introduction
Session II
Chapter 16 – XQuery

2. Outline XQuery Introduction XQuery Functions
Composing and XQuery Document
Identifying a Source Document
Using Path Expressions
FLWOR Expression
XQuery Syntax
XQuery Functions
Add
Select
Conditional Expressions
User Defined Functions
Joining Data Sources
XQuery and Databases
8/1/2014
Copyright © Carl M. Burnett

3. XQuery Introduction XQuery is to XML what SQL is to database tables.
XQuery is designed to query XML data
Extract information to use in a Web Service
Generate summary reports
Transform XML data to XHTML
Search Web documents for relevant information
8/1/2014
Copyright © Carl M. Burnett

4. Composing and XQuery Document
xquery version "1.0";
"Hello World!"
xquery version "1.0";
"Everyone count down:",
reverse(1 to 10),
"Blastoff!"
xquery version "1.0";
<countdown>{reverse(1 to 10)}</countdown>
8/1/2014
Copyright © Carl M. Burnett

5. Identifying a Source Document
xquery version "1.0";
doc("wonders-master.xml")
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Copyright © Carl M. Burnett

6. Using Path Expressions
xquery version "1.0";
doc("wonders-master.xml")/ancient_wonders/wonder/location
8/1/2014
Copyright © Carl M. Burnett

7. FLWOR Expression FLWOR - "For, Let, Where, Order by, Return".
“for” clause selects elements into a variable called $x.
“where” clause selects only elements with a specified.
“order” clause defines the sort-order.
“return” clause specifies what should be returned.
8/1/2014
Copyright © Carl M. Burnett

8. FLWOR Expression Books.xml wonders-master.xml xquery version "1.0";
for $wndr in doc("wonders-master.xml")/ancient_wonders/wonder
where contains($wndr/location, "Turkey")
return $wndr/name
Books.xml
xquery version "1.0";
for $x in doc("books.xml")/bookstore/book
where $x/price>30
order by $x/title
return $x/title
8/1/2014
Copyright © Carl M. Burnett

9. XQuery Syntax XQuery is case-sensitive
XQuery elements, attributes, and variables must be valid XML names
An XQuery string value can be in single or double quotes
An XQuery variable is defined with a $ followed by a name, e.g. $bookstore
XQuery comments are delimited by (: and :), e.g. (: XQuery Comment :)
8/1/2014
Copyright © Carl M. Burnett

10. XQuery Functions XQuery Conditional Expressions XQuery Comparisons
1. General comparisons: =, !=, <, <=, >, >=
2. Value comparisons: eq, ne, lt, le, gt, ge
for $x in doc("books.xml")/bookstore/book
return if
then <child>{data($x/title)}</child>
else <adult>{data($x/title)}</adult>
> 10
gt 10
XQuery Functions
8/1/2014
Copyright © Carl M. Burnett

11. Joining Data Sources xquery version "1.0"; for $wndr in
doc("wonders-master.xml")/ancient_wonders/wonder
for $quake in doc("earthquake_data.xml")/earthquakes/occurrence
where $quake[cities_affected/city = $wndr/location]
return data($quake/date))
8/1/2014
Copyright © Carl M. Burnett

12. XQuery and Databases xquery version "1.0";
let $cntry_medals := collection("olympics.medals")/*
let $total_gold := sum(data($cntry_medals/gold))
let $total_silver := sum(data($cntry_medals/silver))
let $total_bronze := sum(data($cntry_medals/bronze))
let $total_medals := $total_gold + $total_silver + $total_bronze
return (
"Total gold medals awarded:", $total_gold,
"Total silver medals awarded:", $total_silver,
"Total bronze medals awarded:", $total_bronze,
"Total medals awarded:", $total_medals )
8/1/2014
Copyright © Carl M. Burnett

13. Review XQuery Introduction XQuery Functions
Composing and XQuery Document
Identifying a Source Document
Using Path Expressions
FLWOR Expression
XQuery Syntax
XQuery Functions
Add
Select
Conditional Expressions
User Defined Functions
Joining Data Sources
XQuery and Databases
Next – Chapter 14 - XSLT 2.0
8/1/2014
Copyright © Carl M. Burnett