Multiple for loops implementation in XQuery - xquery

Question

Below is my sample XML
<catalog>
<book>
<author>Matthew</author>
<title>XML Developer's Guide</title>
<genre>Computer</genre>
<price>44.95</price>
<publish_date>2000-10-01</publish_date>
<description>An in-depth look at creating applications
with XML.</description>
<storeno>123</storeno>
</book>
<book>
<author>Ralls, Kim</author>
<title>Rain Fantasy</title>
<genre>Fantasy</genre>
<price>5.95</price>
<publish_date>2000-12-16</publish_date>
<description>A former</description>
<storeno>123</storeno>
</book>
<book>
<author>zxcv</author>
<title>Maeve</title>
<genre>Fantasy</genre>
<price>5.95</price>
<publish_date>2000-11-17</publish_date>
<description>After the collapse of a nanotechnology</description>
<storeno>123</storeno>
</book>
<book>
<author>zxcv</author>
<title>Legacy</title>
<genre>Fiction</genre>
<price>5.95</price>
<publish_date>2001-03-10</publish_date>
<description>In post-apocalypse</description>
<storeno>123</storeno>
</book>
<book>
<author>Corets, Eva</author>
<title>The</title>
<genre>Fiction</genre>
<price>5.95</price>
<publish_date>2001-09-10</publish_date>
<description>The two daughters</description>
<storeno>123</storeno>
</book>
<book>
<author>Horror</author>
<title>Horror</title>
<genre>Horror</genre>
<price>4.95</price>
<publish_date>2000-09-02</publish_date>
<description>When abc meets xyz</description>
<storeno>123</storeno>
</book>
<book>
<author>Knorr, Stefan</author>
<title>Creepy Crawlies</title>
<genre>Horror</genre>
<price>4.95</price>
<publish_date>2000-12-06</publish_date>
<description>An anthology of horror stories about roaches,
centipedes, scorpions and other insects.</description>
<storeno>123</storeno>
</book>
<book>
<author>O'Brien, Tim</author>
<title>kids ganes</title>
<genre>story</genre>
<price>36.95</price>
<publish_date>2000-12-09</publish_date>
<description>Microsoft's .NET initiative is explored in
detail in this deep programmer's reference.</description>
<storeno>123</storeno>
</book>
<book>
<author>O'Brien, Tim</author>
<title>MSXML3: A Comprehensive Guide</title>
<genre>computer</genre>
<price>36.95</price>
<publish_date>2000-12-01</publish_date>
<description>The abc</description>
<storeno>123</storeno>
</book>
<book>
<author>Galos, Mike</author>
<title>Visual Studio 7: A Comprehensive Guide</title>
<genre>story</genre>
<price>49.95</price>
<publish_date>2001-04-16</publish_date>
<description>Microsoft Visual Studio</description>
<storeno>123</storeno>
</book>
</catalog>
and I need an XQuery that returns
<titles>
need the first instance of the title where the genre is “Fantasy”
need all the titles concatenated where the genre is “Computer”
need all the titles concatenated where the genre is “Fiction”
need the first instance of the title where the genre is “Story”
</ titles >
example:( Rain Fantasy, XML Developer's Guide………………, Legacy……………….., kids ganes)
Note: the case can be ignored in the above for comparison.
Here is what we are trying
<Titles>
let $fan := $catalog /book[genre = ‘Fantasy’][1]/title
let $stry := $catalog /book[genre = ‘Story’][1]/title
for $comp in $catalog /book[genre ='Computer']/title
return concat($comp, “”)
for $fict in $catalog /book[genre ='Fiction']/title
return concat($fict, “”)
concat($fan, $comp, $fict, $stry)
</Titles>
we are facing issues in multiple for loops implementation.
Any help is really appreciated.
Thanks in advance

Answer 1

From the question and the comments you seem to want something like this:
<Titles>
{
for $genre in distinct-values($catalog/book/genre)
let $books := $catalog/book[genre=$genre]
let $retval := if($genre=("Fantasy","Story")) then $books[1]/title else $books/title
return data($retval)
}
</Titles>
With your input, the result this gives is:
<Titles>XML Developer's Guide Rain Fantasy Legacy The Horror Creepy Crawlies kids ganes Visual Studio 7: A Comprehensive Guide MSXML3: A Comprehensive Guide</Titles>
My gut tells me you probably don't want the data() part though. Without it you get:
<Titles>
<title>XML Developer's Guide</title>
<title>Rain Fantasy</title>
<title>Legacy</title>
<title>The</title>
<title>Horror</title>
<title>Creepy Crawlies</title>
<title>kids ganes</title>
<title>Visual Studio 7: A Comprehensive Guide</title>
<title>MSXML3: A Comprehensive Guide</title>
</Titles>