XPath: is it possible to combine queries

Question

Consider the following XML:

<root>
  <steps>
    <step>1</step>
    <step>2</step>
    <step>3</step>
    <step>4</step>
  </steps>
  <stepDetails step="1">Details</stepDetails>
  <stepDetails step="2">Details</stepDetails>
  <stepDetails step="3">Details</stepDetails>
</root>

What I need to do is find all the steps that do not have corresponding stepDetails. In the above example, only the "<step>4</step>" node would be returned.

Now, I know I can do that by querying all the steps, iterating through the collection and performing another query for each iteration. I'm hoping that there is a way of doing that with just one query. Perhaps using something like SQL's IN statement and a sub-query.

Any ideas or tips would be most appreciated.

thnx, Christoph

Answer 1

Try this:

/root/steps/step[not(. = /root/stepDetails/@step)]