This is one of the uglier warts in XQuery.
http://www.w3.org/TR/xquery/#id-flwor-expressions and
http://www.w3.org/TR/xquery/#prod-xquery-OrderModifier specify that
OrderModifier is a literal token, not a variable or an expression. So
it's tricky to write dynamic sorts.
But here is one approach, taking advantage of multiple OrderSpec
expressions:
let $ascending := false()
for $i in 1 to 10
order by
if ($ascending) then $i else () ascending,
if ($ascending) then () else $i descending
return $i
=>
10 9 8 7 6 5 4 3 2 1
Another technique is to build a query with the desired sorting, then
xdmp:eval() it. That's a very flexible approach, but somewhat
error-prone. If you go down that road, be sure to use external variables
to guard against escaping problems and query injections.
-- Mike
Shannon Scott Shiflett wrote:
hello,
is it possible in xquery flwor to use a conditional expression as the
order modifier of the order by clause? i would like to specify
"ascending" or "descending" dynamically.
thanks,
shannon
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