On 02.05.2019 14:55, Costello, Roger L. costello(_at_)mitre(_dot_)org wrote:
At the bottom of this message is my XML document. I need an XPath 2.0
expression that returns the result of this query:
Are there any book titles with more than
one binding? If yes, then show the first book
for each binding.
For the below XML document, the query should return these two books:
<Book>
<Author>Sally Smith</Author>
<Title>XYZ</Title>
<Binding>hardcover</Binding>
<Count>1</Count>
<Description>lo lo lo ..</Description>
</Book>
<Book>
<Author>Sally Smith</Author>
<Title>XYZ</Title>
<Binding>softcover</Binding>
<Count>1</Count>
<Description>do do do ..</Description>
</Book>
Notice that the two books have the same author and title but different binding
(hardcover versus softcover).
This XPath 2.0 expression seems to work:
for $i in /Bookstore/BookTitle/Book[1],
$j in /Bookstore/BookTitle/Book[1] return
if (($i ne $j)
and ($i/Author eq $j/Author)
and ($i/Title eq $j/Title)
and ($i/Binding ne $j/Binding)
and ($i = $j/preceding::Book))
then ($i, $j)
else ()
That expression seems awfully complicated. Is there a simpler expression? If
there isn't a simpler expression, then do you see anything missing in the
expression (i.e., something that the expression doesn't take into
consideration)?
That seems more like a job for XSLT or XQuery, if I have grasped the
problem correctly then in XQuery it would reduce itself to
for $book in Bookstore/BookTitle/Book[1]
group by $author := $book/Author,
$title := $book/Title,
$binding := $book/binding
where tail($book)
return $book
As for your XPath, I think that instead of
$i ne $j
you rather want
not($i is $j)
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