Summary Here we’ll see some more of the XQuery 1.0 syntax, and look at some examples of the most important structures.

Additional information

Path expressions are simply XPath expressions. The most simple Path expression is “1”. A more practical example is: document("bib.xml")//book[2~//author This query finds each and every author from the second book in the document “bib.xml”. As you can see, the document points to a specific document here. The argument is a name of the document which is part of the XQuery Document Collection. We’ll see later how you can point to more than one document in a query, or simply query the whole collection. The output could look like: <?xml version="1.0"?> <author> <last>Stevens</last> <first>W.</first> </author> Element constructors are used when you want to create elements to be part of the output. An example is: <customer> <order> { (document("bib.xml")//bib/book[author/last="Stevens"~) } </order> </customer> This query finds the book of which the author’s Last Name begins with “Stevens”. It creates a fully well-formed XML document whatever the output is from the query within the brackets. This is useful when we want to perform an XSL Transformation on it later: you need the well-formedness, otherwise you’ll get an error from the XSLT Engine. FLWR expressions are one of the most powerful syntax structures of XQuery 1.0. It is pronounced “flower”, but actually FLWR stands for “FOR, LET, WHERE, and RETURN clauses”. A simple example could be: FOR $b IN document("bib.xml")/bib/book WHERE $b/publisher/text() = "Addison-Wesley" AND $b/@year = "1994" RETURN $b/title This query returns us the book titles published by “Addison-Wesley” in the year “1994”. Another, a bit more complex query could be: <author_list> { FOR $a IN distinct(document("bib.xml")//author) RETURN <author> <name> {$a/text()} </name> { FOR $b IN document("bib.xml")//book[author=$a~ RETURN $b/title } </author> } </author_list> Note the use of brackets which indicate an individual processing unit. If you leave them out, XQuery will treat the text within the brackets as simple text and output it “as-is” without actually processing it. If, however, the syntax rules are broken, then XQuery will generate an error. For sorting, or controlling the order of elements in a result sequence, Xquery offers the SORTBY clause. It is used like this: document("bib.xml")//book[price>100~ SORTBY (author[1~,title) Here we see basically a document() function specifying a document to search, a Path expression, and then a SORTBY clause which sorts the output result tree by first author and within that list it sorts the result by title, in descending (default) order. Expressions involving operators and functions, Conditional expressions, Quantified expressions, Expressions that test or modify datatypes, Functions, User-defined datatypes, Operations on datatypes, and Query Module Structure are all syntax types which describe and extend XQuery features. Examples of some of them can be found in the above examples. XQuery is still in it's initial stage. There are still an impressive number of open issues. One part which is still under development is XQuery's update capabilities. This will include at least INSERT, DELETE, and REPLACE clauses, of which some examples follow here. Example 1. An example of the syntax of an INSERT query could be: FOR $e IN /emp INSERT <n_skills> count($e/skill) </n_skills> BEFORE $e/skill[1~ Example 2. One example of a DELETE query could be as follows: DELETE FOR $e IN /emp/[job = "Programmer"~,$s IN $e/skill WHERE $s/rating < 4 OR $s/cert_date < date("1995-01-01") DELETE $s Example 3. And finally one query example with REPLACE: REPLACE FOR $e IN /emp WHERE $e/empno = "1234” REPLACE $e/job WITH <job> "Broom Tester" </job>

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<menus> <menu ID="1"> <title>TECHNICAL LINKS</title> <top>50</top> <width>250</width> <FontFace>Verdana</FontFace> <FontSize>2</FontSize> <ColorTit>DarkBlue</ColorTit> <FontColorTit>White</FontColorTit> <ColorSep>DarkBlue</ColorSep> <FontColorSep>White</FontColorSep> <ColorOpt>White</ColorOpt> <ColorOptOver>Yellow</ColorOptOver> <separator ID="1" Description="XML Links"> <option ID="1" Description="W3C" url="http://www.w3c.org"/> <option ID="2" Description="VBXML" url="http://www.vbxml.com"/> <option ID="3" Description="XML.Com" url="http://www.xml.com"/> </separator> <separator ID="3" Description="VB Links"> <option ID="1" Description="Randy Birch" url="http://www.mvps.org/vbnet/"/> <option ID="2" Description="Karl E. Peterson's" url="http://www.mvps.org/vb/"/> </separator> <separator ID="2" Description="Access Links"> <option ID="1" Description="My Home Page" url="http://www.geocities.com/pmpg98_pt"/> <option ID="2" Description="Dev Ashish" url="http://www.mvps.org/access"/> <option ID="3" Description="Stephen Lebans" url="http://www.lebans.com"/> </separator> </menu> <menu ID="2"> <title>OTHER LINKS</title> <top>300</top> <width>100</width> <FontFace>Verdana</FontFace> <FontSize>2</FontSize> <ColorTit>Red</ColorTit> <FontColorTit>black</FontColorTit> <ColorSep>yellow</ColorSep> <FontColorSep>black</FontColorSep> <ColorOpt>White</ColorOpt> <ColorOptOver>red</ColorOptOver> <separator ID="1" Description="Music"> <option ID="1" Description="AMG" url="http://www.allmusic.com"/> <option ID="2" Description="CDDB" url="http://www.cddb.com/"/> <option ID="3" Description="MP3.Com" url="http://www.mp3.com/"/> </separator> <separator ID="2" Description="Cinema"> <option ID="1" Description="IMDB" url="http://www.imdb.com/"/> </separator> </menu> </menus>

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