xQuery how to merge two list into one? - xpath

Question

I have an XML document:
<resultsets>
<row>
<emp_no>10001</emp_no>
<first_name>Georgi</first_name>
<last_name>Facello</last_name>
</row>
<row>
<emp_no>10002</emp_no>
<first_name>Bezalel</first_name>
<last_name>Simmel</last_name>
</row>
<row>
<emp_no>10003</emp_no>
<first_name>Parto</first_name>
<last_name>Bamford</last_name>
</row>
</resultsets>
Currently, my code is as follows:
let $first := doc("db/apps/flowq/index/employees.xml")//first_name
let $last := doc("db/apps/flowq/index/employees.xml")//last_name
My question is, is it possible ONLY use $first and $last to generate the following result?
<row>
<first_name>Georgi</first_name>
<last_name>Facello</last_name>
</row>
<row>
<first_name>Bezalel</first_name>
<last_name>Simmel</last_name>
</row>
<row>
<first_name>Parto</first_name>
<last_name>Bamford</last_name>
</row>
Basically, if we have two lists of nodes same size, how can we merge them one by one? I have tried
($first_name, $last_name) and ($first_name union $last_name) but doesn't work,
thanks!

Answer 1

And of course for FP afficionados there's the basic recursive function:
declare function local:merge($s1, $s2) {
if ($s1 and $s2)
then (<row>{head($s1), head($s2)}</row>,
local:merge(tail($s1), tail($s2)))
else ()
}

Answer 2

It is a bit odd that you first extract the two different sequences from the same document but in general if you want positional merging then using for $item at $pos can help:
let $first := (
<first_name>Georgi</first_name>,
<first_name>Bezalel</first_name>,
<first_name>Parto</first_name>),
$second := (
<last_name>Facello</last_name>,
<last_name>Simmel</last_name>,
<last_name>Bamford</last_name>
)
return for $name at $pos in $first
return
<row>
{$name, $second[$pos]}
</row>
http://xqueryfiddle.liberty-development.net/eiQZDbb
Or use higher-order for-each-pair:
let $first := (
<first_name>Georgi</first_name>,
<first_name>Bezalel</first_name>,
<first_name>Parto</first_name>),
$second := (
<last_name>Facello</last_name>,
<last_name>Simmel</last_name>,
<last_name>Bamford</last_name>
)
return for-each-pair($first, $second, function($f, $s) { <row>{$f, $s}</row>})