Xquery to return distinct values in xml

Question

Hi,
I have a requirement, where in i have to get distinct values from an xml file.
EX: Input
<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<Main xmlns="http://www.abc.org.com/FormDetails">
<abcd first="1" second="2"/>
<Fruits>
<fruit name="banana" color="green">
<fruit name="apple" color="red">
<fruit name="grape" color="green">
<fruit name="apple" color="red">
<fruit name="banana" color="green">
<fruit name="apple" color="red">
<fruit name="grape" color="green">
<fruit name="orange" color="orange">
<fruit name ="lemon" color="yellow">
</Fruits>
<Fruits>
<fruit name="banana" color="green">
<fruit name="apple" color="red">
<fruit name="grape" color="green">
<fruit name="apple" color="red">
<fruit name="banana" color="green">
<fruit name="apple" color="red">
<fruit name="grape" color="green">
<fruit name="orange" color="orange">
<fruit name ="lemon" color="yellow">
</Fruits>
<Fruits>
<fruit name="banana" color="green">
<fruit name="apple" color="red">
<fruit name="grape" color="green">
<fruit name="apple" color="red">
<fruit name="banana" color="green">
<fruit name="apple" color="red">
<fruit name="grape" color="green">
<fruit name="orange" color="orange">
<fruit name ="lemon" color="yellow">
</Fruits>
</Main>
Required output: String
banana = green|apple = red| grape=green|orange=orange|lemon=yellow
I have used this xquery:
declare namespace xf = "http://tempuri.org/abcorg/Transformations/Distinct_Fruits/";
declare namespace ns = "http://www.abc.org.com/FormDetails";
declare function xf:Distinct_Fruits($fruits as element(ns:Main))
as xs:string{
for $d in distinct-values($fruits//ns:fruit/@name)
return "{$d} ="
for $e in distinct-values($fruits//ns:fruit/@color)
return "{$e}|"
declare variable $fruitsas element(ns:Main) external;
xf:Distinct_Member($fruits)
I am getting error like:
Error executing the XQuery transformation: line 11, column 1: {err}FORG0005: expected exactly one item, got 2+ items
Please let me know where It went wrong.
Thanks..
Edited by: user12679330 on Jul 12, 2011 4:47 AM

Answer 1

Hi,
Please let me know where It went wrong.The function's return value is declared as a string but you're actually returning sequences of string literals.
One way to achieve that is using string-join function :
(here for testing purpose, I used an external $doc variable)
declare namespace xf = "http://tempuri.org/abcorg/Transformations/Distinct_Fruits/";
declare default element namespace "http://www.abc.org.com/FormDetails";
declare function xf:Distinct_Fruits( $fruits as element(Fruits)* )
as xs:string
string-join(
   for $d in distinct-values($fruits/fruit/@name)
   return concat($d, " = ", $fruits/fruit[@name=$d][1]/@color)
, "|"
xf:Distinct_Fruits($doc/Main/Fruits)Note that I assumed that a fruit with a given name will always have the same color.
If that's not the case and you might have something like :
<Main>
<abcd first="1" second="2"/>
<Fruits>
  <fruit name="banana" color="green"/>
  <fruit name="apple" color="red"/>
  <fruit name="grape" color="green"/>
  <fruit name="apple" color="red"/>
  <!-- here is a red banana! -->
  <fruit name="banana" color="red"/>
  <fruit name="apple" color="red"/>
  <fruit name="grape" color="green"/>
  <fruit name="orange" color="orange"/>
  <fruit name ="lemon" color="yellow"/>
</Fruits>
</Main>then the solution is to use deep-equal function to test if two nodes are identical (as per their values, attributes and children) :
declare function xf:Distinct_Fruits( $fruits as element(Fruits) )
as xs:string
string-join(
   for $i in $fruits/fruit
   let $f := $i[not(some $x in $i/preceding-sibling::fruit satisfies fn:deep-equal($x,.))]
   where ($f)
   return concat($f/@name, " = ", $f/@color)
, "|"
};which gives :
banana = green|apple = red|grape = green|banana = red|orange = orange|lemon = yellowEdited by: odie_63 on 12 juil. 2011 14:43 - changed first example to reflect sample modification