I am using the following file:
<bookstore>
<book category="COOKING">
<title lang="en">Everyday Italian</title>
<author>Giada De Laurentiis</author>
<year>2005</year>
<price>30.00</price>
</book>
<book category="CHILDREN">
<title lang="en">Harry Potter</title>
<author>J K. Rowling</author>
<year>2005</year>
<price>29.99</price>
</book>
<book category="WEB">
<title lang="en">XQuery Kick Start</title>
<author>James McGovern</author>
<author>Per Bothner</author>
<author>Kurt Cagle</author>
<author>James Linn</author>
<author>Vaidyanathan Nagarajan</author>
<year>2003</year>
<price>49.99</price>
</book>
<book category="WEB">
<title lang="en">Learning XML</title>
<author>Erik T. Ray</author>
<year>2003</year>
<price>39.95</price>
</book>
</bookstore>
I am using the following query to get the names from the XML document
for $x at $i in doc("bookstore.xml")/bookstore/book/*
return fn:distinct-values(name($x))
I am getting following results:
title
author
year
price
title
author
year
price
title
author
author
author
author
author
year
price
title
author
year
price
Instead I just want the distinct one as shown below.
title
author
year
price
I believe I messed up the for loop. Can someone help me with a fix for this? I tried using distinct-values(). No luck.
You were calling distinct-values()
within the for loop, once for each item in the sequence returned by your expression. Instead pass the result of for
expression to distinct-values()
:
fn:distinct-values(
for $x at $i in doc("bookstore.xml")/bookstore/book/*
return name($x)
)
One side note: node-name()
or local-name()
are generally recommended over name()
. Use the former when you need the qualified name of the element and the latter when you only want the string value.
name($x)
contains name of element that currently referenced by variable $x
. And $x
always references one element at a time, so calling distinct-values()
on name($x)
won't be useful. Instead, you want to call distinct-values()
on a collection containing all the elements name, like for example :
let $result :=
for $x at $i in doc("bookstore.xml")/bookstore/book/*
return name($x)
return fn:distinct-values($result)
This can also be achieved using plain XPath expression as follow :
distinct-values(doc("bookstore.xml")/bookstore/book/*/name(.))
You may also try simplest one
let $x := doc("bookstore.xml")/bookstore/book
return distinct-values($x/name())
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