How to express an Inner Join in XSLT?

[craigj]

My source XML is as follows:

Code: Select all

<Data>

  <Car registration="1" type="Ford" />

  <Car registration="2" type="Volkswagen" />

  <Car registration="3" type="Volkswagen" />

  <Car registration="4" type="Porsche" />

  <Car registration="5" type="Porsche" />

  <Journey car="1" distance="10" />

  <Journey car="1" distance="15" />

  <Journey car="3" distance="5" />

  <Journey car="2" distance="6" />

</Data>

I want to calculate 'The total distance covered by all Porsche cars'.

My query should look something like:

sum(/Data/Journey[SOMECONDITION]/@distance)

(where SOMECONDITION joins the journeys to the associated car and checks that @type = 'Porsche')

---

I'm just not quite sure of how to express this in XSLT. Any help would be appreciated.

[craigj]

Note: I realise the example source code I provided will produce a result of zero for 'Distance covered by all Porsche cars', but hopefully you get the idea.

The results would be:
Ford: 25
Volkswagen: 11
Porsche: 0

[craigj]

Ok, I managed to solve it using 2 lines:

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<xsl:variable name="volkswagenCars" select="/Data/Car[@type = 'Volkswagen']" />

<xsl:variable name="totalVolkswagenDistance" select="sum(/Data/Journey[@car = $volkswagenCars/@registration]/@distance)" />

Can this be expressed in one line?

[sorin_ristache]

Hello,

I don't think you can express it in one line if you want to process all the Car elements. For example:

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<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="2.0">

  <xsl:template match="Data">

    <distances>

      <xsl:for-each-group select="Car" group-by="@type">

        <car type="{current-grouping-key()}" distance="{sum(for $i in current-group() return

          following-sibling::Journey[@car = $i/@registration]/@distance)}"/>

      </xsl:for-each-group>

    </distances>

  </xsl:template>

</xsl:stylesheet>

Regards,
Sorin

[sorin_ristache]

Actually the condition can be written as a single line (if you ignore the xsl:for-each-group element):

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  <xsl:for-each-group select="Car" group-by="@type">

      <car type="{current-grouping-key()}" distance="{sum(following-sibling::Journey[@car = current-group()/@registration]/@distance)}"/>

  </xsl:for-each-group>

Regards,
Sorin