basex - How to find the lowest common ancestor of two nodes in XQuery? -

suppose input xml

<root> <entry>     <title>test</title>     <author>me</author>   </entry> </root> 

i find lowest common ancestor of title , author. tried following code in basex:

 let $p := doc('t.xq')//title,   $q := doc('t.xq')//author,   $cla := ($p/ancestor-or-self::node() intersect $q/ancestor-or-self::node())   return      $cla 

but returns nothing (blank output).

your code works totally fine me, apart returning all common ancestors.

the last common ancestor

since they're returned in document order , last common ancestor must last node, extend [last()] predicate.

declare context item := document {   <root>     <entry>       <title>test</title>       <author>me</author>     </entry>   </root> };  let $p := //title,      $q := //author,      $cla := ($p/ancestor-or-self::node() intersect $q/ancestor-or-self::node())[last()] return      $cla 

files , databases

if query posted not return anything, might working on file t.xq. intersect requires nodes compared in same database, each invocation of doc(...) on file creates new in-memory database. either create database in basex contents, or like

declare variable $doc := doc('t.xq'); 

and replace subsequent doc(...) calls $doc (which references single in-memory database created file).