Demo of how to grab all `<affiliate>` nodes with the `@refID` as specified by the `$refID` variable – *or*, if the $refID variable is empty, take all `<affiliate>`s ...

affiliates.xml

<root>
  <affiliate refID="1200">1200</affiliate>
	<affiliate refID="1201">1201</affiliate>
	<affiliate refID="1202">1202</affiliate>
	<affiliate refID="1203">1203</affiliate>
	<affiliate refID="1204">1204</affiliate>
	<affiliate refID="1205">1205</affiliate>
	<affiliate refID="1206">1206</affiliate>
	<affiliate refID="1207">1207</affiliate>
	<affiliate refID="1208">1208</affiliate>
</root>

affiliates.xslt

<?xml version="1.0" encoding="utf-8" ?>
<xsl:stylesheet
  version="1.0"
	xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
>

	<xsl:variable name="refID" select="1202" />
	<xsl:variable name="affiliates" select="/root/affiliate" />

	<xsl:template match="root">
		<result>
			<xsl:apply-templates select="
				$affiliates[normalize-space($refID)][@refID = $refID]
				|
				$affiliates[not(normalize-space($refID))]
			" />
		</result>
	</xsl:template>
	
	<xsl:template match="affiliate">
		<p><xsl:value-of select="." /></p>
	</xsl:template>

</xsl:stylesheet>

—To test the empty value for $refID, either use "/.." (guaranteed to always be an empty set) or '' :

<xsl:variable name="refID" select="/.." />

or:

<xsl:variable name="refID" select="''" />