XSLT to remove duplicates completely - xslt

Question

I know there are solutions plenty to remove duplicates, but this one is slightly different. I need to remove the element from the output if it is a duplicate.
Input:
<SanctionList>
<row>
<PersonId>1000628</PersonId>
<PersonId>1000634</PersonId>
<PersonId>1113918</PersonId>
<PersonId>1133507</PersonId>
<PersonId>1113918</PersonId>
</row>
</SanctionList>
Output expected:
<SanctionList>
<row>
<PersonId>1000628</PersonId>
<PersonId>1000634</PersonId>
<PersonId>1133507</PersonId>
</row>
</SanctionList>
Here is what I tried but the parser returns 1 for each of the groups. Shouldnt it return 2 for PersonId 1113918 since it appears twice in the list?
<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" xmlns:xs="http://www.w3.org/2001/XMLSchema" version="2.0">
<xsl:strip-space elements="*"/>
<xsl:template match="node()|#*">
<xsl:copy>
<xsl:apply-templates select="node()|#*"/>
</xsl:copy>
</xsl:template>
<xsl:template match="SanctionList">
<xsl:for-each-group select="row" group-by="PersonId">
<xsl:text> Count for </xsl:text>
<xsl:value-of select="current-grouping-key()" />
<xsl:text> is </xsl:text>
<xsl:value-of select="count(current-group())" />
</xsl:for-each-group>
</xsl:template>
</xsl:stylesheet>
Thanks kindly!

Answer 1

I know there are solutions plenty to remove duplicates, but this one
is slightly different. I need to remove the element from the output if
it is a duplicate
Use this short and simple transformation (both in XSLT 2.0 and XSLT 1.0):
<xsl:stylesheet version="2.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:output omit-xml-declaration="yes" indent="yes"/>
<xsl:strip-space elements="*"/>
<xsl:key name="kPersonByVal" match="PersonId" use="."/>
<xsl:template match="node()|#*">
<xsl:copy>
<xsl:apply-templates select="node()|#*"/>
</xsl:copy>
</xsl:template>
<xsl:template match="PersonId[key('kPersonByVal', .)[2]]"/>
</xsl:stylesheet>
when the transformation is applied on the provided XML document:
<SanctionList>
<row>
<PersonId>1000628</PersonId>
<PersonId>1000634</PersonId>
<PersonId>1113918</PersonId>
<PersonId>1133507</PersonId>
<PersonId>1113918</PersonId>
</row>
</SanctionList>
the wanted, correct result is produced:
<SanctionList>
<row>
<PersonId>1000628</PersonId>
<PersonId>1000634</PersonId>
<PersonId>1133507</PersonId>
</row>
</SanctionList>
Explanation:
A wellknown design pattern for copying an existing XML document and deleting/replacing/inserting some nodes into the copy, is by overriding the identity rule.
In this particular case the task is to delete <PersonId> elements. This is done by providing a matching template with no (empty) body.
The criterion for deletion is that the element must have a duplicate -- that is, at least two <PersonId> elements must exist, having the same string value. This is most conveniently done using an <xsl:key> declaration and the key() function to get all elements with the same string value.
Finally, in the match pattern of the empty (deleting) template we check if the node-set of equally-valued elements has a second element.
Note: You can learn more about the <xsl:key> declaration and the key() function in module 9 of my Pluralsight training course "XSLT 2.0 and 1.0 foundations"