Its been a while since I’ve last posted. I’ve setup the latest version of WordPress, and blog via email so hopefully I’ll get more motivated to do something about it…Shorter and sweeter is probably the key.

In this issue – selecting unique values using only XPath v1….and I still don’t completely understand it! 😉

Take the following XPath query I (eventually) wrote:

//product_vertical_classification/row[not(product_type_id=preceding-sibling::row/product_type_id)]/product_type_id/text()

Without giving too much away, the following XML snippet was the cause for concern:

<product_vertical_classification>

      <row>

            <product_type_id>SELFCONTAI</product_type_id>

            <product_type_description>Self Contained</product_type_description>

            <product_sub_type_1_id>SCCABPARK</product_sub_type_1_id>

            <product_sub_type_1_description>Park Cabin</product_sub_type_1_description>

            <product_sub_type_lowest>SCCABPARK</product_sub_type_lowest>

      </row>

      <row>

            <product_type_id>SELFCONTAI</product_type_id>

            <product_type_description>Self Contained</product_type_description>

            <product_sub_type_1_id>SELFCONTAI</product_sub_type_1_id>

            <product_sub_type_1_description>Self Contained</product_sub_type_1_description>

            <product_sub_type_lowest>SELFCONTAI</product_sub_type_lowest>

      </row>

      <row>

            <product_type_id>VANCAMP</product_type_id>

            <product_type_description>Caravan/Camping</product_type_description>

            <product_sub_type_1_id>VANCAMP</product_sub_type_1_id>

            <product_sub_type_1_description>Caravan/Camping</product_sub_type_1_description>

            <product_sub_type_lowest>VANCAMP</product_sub_type_lowest>

      </row>

      <row>

            <product_type_id>VANCAMP</product_type_id>

            <product_type_description>Caravan/Camping</product_type_description>

            <product_sub_type_1_id>VCCARAVAN</product_sub_type_1_id>

            <product_sub_type_1_description>Caravan Park</product_sub_type_1_description>

            <product_sub_type_lowest>VCCARAVAN</product_sub_type_lowest>

      </row>

</product_vertical_classification>

I needed to select a unique list of all product_type_id’s in the XML. Given my limited understanding of XML, I resorted to DevX for assistance and here’s my interpretation of what it’s doing:

1.      Select from all product_vertical_classification elements

2.      Select rows where

a.      The product_type_id is NOT equal to the product id of any row BEFORE this one in the XML

3.      Select the text from element product_type_id from the result set

It’s the preceding-sibling axis that threw me off. Pretty clever actually.

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