[Qexo-general] Duplicates/Distinct-Function

[Sascha Opletal]

I need some distinct-values function for node-values and attribute-values:

I need to combine the attributes c="1" c="2" and c="1" with each other. 
The attribute set
is called C. With two for-loops i built CxC, which is described in the 
following.

Data is:

<a>
<b c="1">1</b>
<b c="2">2</b>
<b c="1">1</b>
</a>

First Xquery is:

for $a in doc("data2.xml")/a/b,
  $b in doc("data2.xml")/a/b

return
<result>
{$a}
{$b} </result>

This gives:

<result>
<b c="1">1</b>
<b c="1">1</b>
</result><result>
<b c="1">1</b>
<b c="2">2</b>
</result><result>
<b c="1">1</b>
<b c="1">1</b>
</result><result>
<b c="2">2</b>
<b c="1">1</b>
</result><result>
<b c="2">2</b>
<b c="2">2</b>
</result><result>
<b c="2">2</b>
<b c="1">1</b>
</result><result>
<b c="1">1</b>
<b c="1">1</b>
</result><result>
<b c="1">1</b>
<b c="2">2</b>
</result><result>
<b c="1">1</b>
<b c="1">1</b>
</result>


Instead of this i need only equal pairs like this:

<result>
<b c="1">1</b>
<b c="1">1</b>
</result><result>
<b c="1">1</b>
<b c="1">1</b>
</result><result>
<b c="2">2</b>
<b c="2">2</b>
</result><result>
<b c="1">1</b>
<b c="1">1</b>
</result><result>
<b c="1">1</b>
<b c="1">1</b>
</result>

so i added the line

where $a/@c = $b/@c

to the for expression.

Now to be happy i need something to make sure no repeating takes place, 
if there is more than one equal
attribute...the attributes are 1 2 1 and the last "1" is combined again 
and gives the same result as the
first element "1"

The desired result would be:

<result>
<b c="1">1</b>
<b c="1">1</b>
</result><result>
<b c="2">2</b>
<b c="2">2</b>
</result>

Is there something like a set function where i can add an element and 
check if it is already in there
or something else to achieve this?