CODEWITHSUNDEEP
xpath
Matthias Petri
Matthias Petri

Reputation: 23

xpath syntax for semi-joins

I know that I can use xpath to perform joins using the "|" operator. Is there a way to perform semi-joins in xpath like for example: 

book[author = article/author]/title

If semi-joins exist, what would the output of the query above look like. Does it just output the title element of each book that has an author who also authored an article?

Upvotes: 2

Views: 578

Answers (2)

Paul Butcher
Paul Butcher

Reputation: 6956

The given query would return the title of each book that contains an article that has been authored by that book's author. Thus, in the context of books below, the only thing returned would be the title element with the text "title 0".

<books>    
 <book>
   <title>Title 0</title>
   <author>Petri, M</author>
   <article>
     <title>Title 1</title>
     <author>Petri, M</author>
   </article>
   <article>
     <title>Title 2</title>
     <author>Butcher, P</author>
   </article>
 </book>

 <book>
    <title>Title 3</title>
    <author>Butcher, P</author>
    <article>
      <title>Title 4</title>
      <author>Petri, M</author>
    </article>
 </book>
</books>

Upvotes: 0

Martin Honnen
Martin Honnen

Reputation: 167706

Maybe you want //book[author = //article/author]/title. With your current attempt book[author = article/author] the article elements would need to be children of the book element which does not seem likely.

Upvotes: 2

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