RE: How to transform flat structure into hierarchical one?
> -----Original Message----- > From: owner-xsl-list@xxxxxxxxxxxxxxxx > [mailto:owner-xsl-list@xxxxxxxxxxxxxxxx]On Behalf Of Kay Michael >> > > Here he does not mean group as in "GROUP BY" but simply as putting > > related records next to each other as in "ORDER BY". Don't > > think in SQL all the time - English is trickier than that. > > > Yes, I was speaking generically. But you can go further than SQL > ordering to > make the transformation easy, for example you can start with a SELECT > DISTINCT and put a list of distinct key values at the start of > the XML file: > it's then easy to work through the distinct values and for each one use > key() to find all the actual records with that value. As the case was presented that would mean executing 2 queries without data duplication savings. I also do not see the possible XSLT becoming much more efficient so... my guess is that it would be slower. But that principle would apply with bulky master data. A classic example is the Invoice/InvoiceRows - onde does not want to duplicate a massive invoice header per each of its rows (wich usualy hold less data than the invoice header). The duplication would produce a huge extra amount of XML to be parsed. > Another way to tackle this problem is not to generate an XML file at all. > Instead the program that queries the database can offer the data > to the XSLT > processor as a stream of SAX events. It's then easy for it to > slip in extra > startElement and endElement events when the key value changes. > That is a damn interesting method. I am not going to use id in my "nice" ADO2.5/MSXML3 framework where so much is already there, but I am planing the move to a Java environment (probably Oracle's) and then... (Yeah... Java is slower but I am not blind to the advantages.) Have fun, Paulo Gaspar (paulo.gaspar@xxxxxxxxxxxx) XSL-List info and archive: http://www.mulberrytech.com/xsl/xsl-list
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