David Kitchen

I’ve frequently encountered the need to produce titles for XSLT produced tables.

For example, given the following XML:
<events>
<event date="2004-11-30 14:00:00" />
<event date="2004-11-30 14:00:00" />
<event date="2003-11-30 14:00:00" />
<event date="2002-11-30 14:00:00" />
</events>


To extract the values “2002″ and “2004″ to format a title such as “Events (2002 > 2004)”.

To do this effectively requires us to extract both the MAX and MIN values, for which we need an XSLT equivalent to the SQL SELECT MAX() and SELECT MIN() functions.

There is a neat trick to do this which can be summed up thus:

• Sort ascending and pick the first node and you have your MIN.
• Sort descending and pick the first node and you have your MAX.

Examples of both, given the above XML are here for your reference.

Obtaining the MIN:
<!-- Create a variable named $minEventDate containing the MIN date -->
<xsl:variable name="minEventDate">
<xsl:for-each select="event">
<xsl:sort select="@date" data-type="text" order="ascending" />
<xsl:if test="position() = 1">
<xsl:value-of select="@date" />
</xsl:if>
</xsl:for-each>
</xsl:variable>


Obtaining the MAX:
<!-- Create a variable named $maxEventDate containing the MAX date -->
<xsl:variable name="maxEventDate">
<xsl:for-each select="event">
<xsl:sort select="@date" data-type="text" order="descending" />
<xsl:if test="position() = 1">
<xsl:value-of select="@date" />
</xsl:if>
</xsl:for-each>
</xsl:variable>