Subject: Re: [xsl] Filter by id and date From: "Tony Graham" <tgraham@xxxxxxxxxx> Date: Mon, 5 Sep 2011 11:18:58 +0100 (IST) |
On Mon, September 5, 2011 10:36 am, Emma Burrows wrote: ... > <items> > <item id='1' date='2011'>Item1</item> > <item id='2' date='2009'>Item2</item> > <item id='3' date='2002'>Item3</item> > <item id='2' date='2011'>Item2</item> > <item id='3' date='2002'>Item3</item> > </items> > > For example, the Xpath in question looks like this right now (long-winded > but more efficient path-finding syntax simplified to // for this example, > and $idref obviously contains a valid id): > > <xsl:value-of select="normalize-space(//item[@id=$idref])"/> > > What is the best way to filter that to return only the item whose @date is > the highest for all items with @id=$idref? The one-line solution is: normalize-space(//item[@id=$item][@date = max(../item[@id=$item]/@date)][1]) Note the '[1]' to get rid of duplicates such as 'Item3' in your example. You've already received a solution from Andrew Welch that first makes a variable for all the possible matching values. That would generally be clearer and easier to understand when you come back to it in six months time. If you have a lot of data with a lot of duplicates in any order, it may be simplest to process the data once to sort it by date and then change your @select to "normalize-space(//item[@id=$idref][1])". BTW, have you looked at using xsl:key? Would it be possible to replace the long and complicated XPath with a xsl:key that indexes the <item> with a key based on, say, the string-join() of the significant variable data from the XPath so you can just lookup the <item>s?) Regards, Tony Graham tgraham@xxxxxxxxxx Consultant http://www.mentea.net Mentea 13 Kelly's Bay Beach, Skerries, Co. Dublin, Ireland -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- XML, XSL FO and XSLT consulting, training and programming
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