Well you could use the same method as described in https://forum.mendix.com/link/questions/7389.
To do this..
It's not really pretty though, the union-operator sounds like a better option but I can't think of a way how to use it correctly here.
Even though you sadly do need an extra concatenated attribute for this I think the removing of duplicates from a list can also be achieved by doing a union of the list on itself. That is a bit less cumbersome than the iteration mentioned in the linked answer.
of Appstore app “ListUtils” a try. It is available in 7.23
like it says in their documentation-tab:
Example 4: List clean-up, removing redundant items
You may want to clean-up a list by removing duplicate items (i.e., items with the same attribute value). This can be achieved by using the Filter function with the following filter to get the unneeded redundant items:
<xsl:for-each-group select="record" group-by="@lastname"> <xsl:if test="count(current-group()) > 1"> <xsl:for-each select="current-group()"> <xsl:if test="position() > 1"> <xsl:copy-of select="."/> </xsl:if> </xsl:for-each> </xsl:if> </xsl:for-each-group>