XQuery "flattening" an element - xquery

Question

I am extracting data from an XML file and I need to extract a delimited list of sub-elements. I have the following:
for $record in //record
let $person := $record/person/names
return concat($record/#uid/string()
,",", $record/#category/string()
,",", $person/first_name
,",", $person/last_name
,",", $record/details/citizenships
,"
")
The element "citizenships" contains sub-elements called "citizenship" and as the query stands it sticks them all together in one string, e.g. "UKFrance". I need to keep them in one string but separate them, e.g. "UK|France".
Thanks in advance for any help!

Answer 1

fn:string-join($arg1 as xs:string*, $arg2 as xs:string) is what you're looking for here.
In your currently desired usage, that would look something like the following:
fn:string-join($record/details/citizenships/citizenship, "|")
Testing outside your document, with:
fn:string-join(("UK", "France"), "|")
...returns:
UK|France
Notably, ("UK", "France") is a sequence of strings, just as a query returning multiple citizenships would likewise be a sequence (the entries in which will be evaluated for their string value when passed to fn:string-join(), which is typed as taking a sequence of strings for its first argument).
Consider the following (simplified) query:
declare context item := document { <root>
<record uid="1">
<person>
<citizenships>
<citizenship>France</citizenship>
<citizenship>UK</citizenship>
</citizenships>
</person>
</record>
</root> };
for $record in //record
return concat(fn:string-join($record//citizenship, "|"), "
")
...and its output:
France|UK