You're using "=" rather than "is" to compare books. That's a dangerous mistake
to make (a) because it gives you the right answer 99% of the time, and (b)
because it's incredibly expensive.
I couldn't think of a better approach with XPath 2.0. As Martin says, it's the
wrong tool for the job.
Michael Kay
Saxonica
On 2 May 2019, at 13:55, Costello, Roger L. costello(_at_)mitre(_dot_)org
<xsl-list-service(_at_)lists(_dot_)mulberrytech(_dot_)com> wrote:
Hello XPath experts!
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)? /Roger
<Bookstore>
<BookTitle>
<Book>
<Author>John Doe</Author>
<Title>ABC</Title>
<Binding>hardcover</Binding>
<Count>1</Count>
<Description>da da da ..</Description>
</Book>
<Book>
<Author>John Doe</Author>
<Title>ABC</Title>
<Binding>hardcover</Binding>
<Count>2</Count>
<Description>za za za ..</Description>
</Book>
</BookTitle>
<BookTitle>
<Book>
<Author>John Doe</Author>
<Title>Foo</Title>
<Binding>softcover</Binding>
<Count>1</Count>
<Description>na na na ..</Description>
</Book>
</BookTitle>
<BookTitle>
<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>hardcover</Binding>
<Count>2</Count>
<Description>ho ho ho ..</Description>
</Book>
</BookTitle>
<BookTitle>
<Book>
<Author>Sally Smith</Author>
<Title>XYZ</Title>
<Binding>softcover</Binding>
<Count>1</Count>
<Description>do do do ..</Description>
</Book>
</BookTitle>
</Bookstore>
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