I would like to calculate the sum of the prices whos attribute (idnr) can be found under params. In this sample case I want the result to be 342 + 13 + 19 + 1200 = 1574.

My problem is matching the PRICE attributes with the ID names. In SQL this would have been solved with nested queries or a JOIN.

How can I solve this problem?

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This is how I want the XSLT code to look like:

<xsl:value-of select="sum(/PRODUCTS/*[Here I'd like to match attribute::idnr with name(/PARAMS/*)]/text())"/>

The XML data:

...

<PARAMS>
 <ID5>on</ID5>
 <NAME>Anders</NAME>
 <ID1>on</ID1>
 <ID2>on</ID2>
 <DEBUG>TRUE</DEBUG>
 <ID8>on</ID8>
</PARAMS>

...

<PRODUCTS>
 <PRICE idnr="ID1">13</PRICE>
 <PRICE idnr="ID2">19</PRICE>
 <PRICE idnr="ID3">23</PRICE>
 <PRICE idnr="ID4">54</PRICE>
 <PRICE idnr="ID5">342</PRICE>
 <PRICE idnr="ID6">756</PRICE>
 <PRICE idnr="ID7">1100</PRICE>
 <PRICE idnr="ID8">1200</PRICE>
</PRODUCTS>

...