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Re: Keys and select distinct - is that the solution ?

Subject: Re: Keys and select distinct - is that the solution ?
From: "Christian Rasmussen" <byggemandbob@xxxxxxxxx>
Date: Sat, 3 Jun 2006 00:36:51 +0200
xslt select distinct values
First of all thanx to both of you for trying to help.
right now I am trying to apply your suggestions....

I am a quite newbie and I am not not sure I understand the muenchian method,
but regarding your last statement Wendell Piez:

I believe it is a many to many relation:

If you look back on my input, you can see that the code 5 for instance
is listed two times in one of the structures (aka tables), and I have
to take that value and look it up somewhere else in the document (aka
another table) and return the value "Ajle".

That is a one to many....

well, I'll go work on those two other suggestions...

- Christian

On 6/3/06, Wendell Piez <wapiez@xxxxxxxxxxxxxxxx> wrote:
Dear Christian,

XSLT 2.0 has a distinct-values() function, which
is useful for this kind of thing, along with its native grouping
constructs.

In XSLT 1.0, it's a fairly standard grouping problem. Usually we de-duplicate a set of nodes by determining which members of the set are the first (in document order) with a given value. In your case, you have to decide whether the value you want to check is the code value, or the name (if they're in a strict one-to-one relation it doesn't matter, and the value is more convenient).

Keys are a very convenient way to de-duplicate
when your data set is large. You can use brute XPath if not.

So:

<xsl:key name="manure-type-codes" match="gr:ManureTypeCode"
   use="."/>

<xsl:key name="manure-type-names" match="gr:ManureTypeName"
   use="../gr:ManureTypeCode"/>

<xsl:template match="gr:ManureTypeCode">
   <xsl:if test="generate-id() =
generate-id(key('manure-type-codes',.)[1])">
<!-- tests true only if the ManureTypeCode is the first with this
value,
          more or less the equivalent of 'select distinct' -->
     <xsl:copy-of select="key('manure-type-names',.)"/>
   </xsl:if>
</xsl:template>

If the codes and names are in a one-to-many or
many-to-many relation, we have to think harder.

I hope this helps!
Wendell

At 05:55 PM 6/2/2006, you wrote:
>Hi experts,
>
>I've been struggling with a problem for several hours now, and I
>cannot find the solution:
>I have an XML document with a elements grouped in elements and
>ManureTypeCodes and datavalues as siblings.
>Then I have - somewhere else - in the document lookup information
>(labels) for the codes.
>These are grouped in elements of ManureTypeCodes and ManureTypeNames
>
>I want to create a template rule which matches the codes and looks up
>the corresponding name and ONLY writes the
>ManureTypeName out once! In RDBMS I would use something like select
>distinct when selecting the codes, but I dont know what the right
>approach is in XSLT.
>
>can someone please help.... on before hand thank you!
>
>my XML:
><eih>
>    <!-- Codes and data  -->
>    <eih:ManureTypeCollection>
>        <eih:ManureTypeStructure>
>            <gr:ManureTypeCode>5</gr:ManureTypeCode>
>            <gr:ElementIdentifier>N</gr:ElementIdentifier>
>            <gr:ElementQuantity>17.0</gr:ElementQuantity>
>        </eih:ManureTypeStructure>
>        <eih:ManureTypeStructure>
>            <gr:ManureTypeCode>5</gr:ManureTypeCode>
>            <gr:ElementIdentifier>P</gr:ElementIdentifier>
>            <gr:ElementQuantity>0.6</gr:ElementQuantity>
>        </eih:ManureTypeStructure>
>        <eih:ManureTypeStructure>
>            <gr:ManureTypeCode>4</gr:ManureTypeCode>
>            <gr:ElementIdentifier>N</gr:ElementIdentifier>
>            <gr:ElementQuantity>17.5</gr:ElementQuantity>
>        </eih:ManureTypeStructure>
>        <eih:ManureTypeStructure>
>            <gr:ManureTypeCode>4</gr:ManureTypeCode>
>            <gr:ElementIdentifier>P</gr:ElementIdentifier>
>            <gr:ElementQuantity> 6.3</gr:ElementQuantity>
>        </eih:ManureTypeStructure>
>    </eih:ManureTypeCollection>
>
>    <!-- look up information for the codes -->
>    <eih:XImanureTypeCollection>
>        <eih:XImanureTypeStructure>
>            <gr:ManureTypeCode>4</gr:ManureTypeCode>
>            <gr:ManureTypeName>Fast gxdning</gr:ManureTypeName>
>        </eih:XImanureTypeStructure>
>        <eih:XImanureTypeStructure>
>            <gr:ManureTypeCode>5</gr:ManureTypeCode>
>            <gr:ManureTypeName>Ajle</gr:ManureTypeName>
>        </eih:XImanureTypeStructure>
>        <eih:XImanureTypeStructure>
>    </eih:XImanureTypeCollection>
></eih>
>
>
>best regards,
>
>Christian Rasmussen
>Denmark

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