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Re: A better way to build a comma-delimited list

Subject: Re: A better way to build a comma-delimited list
From: Joerg Heinicke <joerg.heinicke@xxxxxx>
Date: Wed, 15 May 2002 16:35:21 +0200
select statement comma delimited
Oh sorry. Your mail switched some lights on ;-)

I remember that for-each $dbdef was only for switching into the other document, wasn't it? Then your solution using $p and $l was absolutely correct (in theory). But the problem will still be there. The problem is that the nodeset from the outer for-each (which the last() refers too) is not the output, because of a further condition (the inner for-each). It's really tricky then. If not anybody else has a better solution a recursive approach or at least a step-by-step approach (using following-sibling::*[1]) can be necessary. The following is not using last(), but testing for the first element. It has the same weak point as the other one, but maybe works with your code (the first @dbcolumn must be in $dbdef). Another possibility
is using a variable, which stores the string and a recursive template which removes all leading commas. Hmm, when writing this a got a new idea. When you don't add a comma, but a space before or after a column, you can do a normalize-space on the variable and replace every space with a comma after this:


<xsl:text>select </xsl:text>
<xsl:variable name="string">
<xsl:for-each select="document($pbsdef)/pbsdef/column[not(@dbcolumn=preceding-sibling::column/@dbcolumn)]">
<xsl:variable name="p" select="position()"/>
<xsl:variable name="dbcolumn" select="@dbcolumn"/>
<xsl:for-each select="$dbdef[key('dbdef-cols', $dbcolumn)]">
<xsl:if test="$p != 1">
<xsl:text> </xsl:text>
</xsl:if>
<xsl:value-of select="$dbcolumn"/>
</xsl:for-each>
</xsl:for-each>
</xsl:variable>
<xsl:value-of select="translate(normalize-space($string), ' ', '')"/>


This should result in "select col1,col2,col3".

Regards,

Joerg

John Sands wrote:
Hi Joerg,


<xsl:for-each select="$dbdef[key('dbdef-cols', $dbcolumn)]">
  <xsl:value-of select="$dbcolumn"/>
  <xsl:if test="position() != last()">
    <xsl:text>, </xsl:text>
  </xsl:if>
</xsl:for-each>


I loved the solution because it would fix the problem AND make the
code shorter. Unfortunately it doesn't work because position() and
last() are both 1 so I get:

select col1col2col3

John





-----Original Message-----
From: Joerg Heinicke  <joerg.heinicke@xxxxxx>
Sent: Wednesday, May 15, 2002, 3:15:02 AM,
Subject:  A better way to build a comma-delimited list


Hello John,


>       <xsl:for-each select="$dbdef">
>          <xsl:if test="key('dbdef-cols', $dbcolumn)">
>             <xsl:value-of select="$dbcolumn"/>
>             <xsl:if test="$p &lt; $l">
>                <xsl:text>, </xsl:text>
>             </xsl:if>
>          </xsl:if>
>       </xsl:for-each>


instead of the for-each + if you can write one for-each with predicate:


<xsl:for-each select="$dbdef[key('dbdef-cols', $dbcolumn)]">


Now the correct nodeset is selected and position() and last() will work. But they must refer to the inner for-each, so you can't use $p and $l, but <xsl:if test="position() != last()">.


So, you have then


<xsl:for-each select="$dbdef[key('dbdef-cols', $dbcolumn)]">
  <xsl:value-of select="$dbcolumn"/>
  <xsl:if test="position() != last()">
    <xsl:text>, </xsl:text>
  </xsl:if>
</xsl:for-each>


Regards,


Joerg


John Sands schrieb:

I have some XSLT that builds a SQL select statement from several input
documents. Here's a fragment that builds the column list by getting
each distinct column name from a separate file ($pbsdef) and checking
that is is defined in another file (referenced by variable $dbdef).

  <xsl:text>select </xsl:text>
  <xsl:for-each select="document($pbsdef)/pbsdef/column[not(@dbcolumn=preceding-sibling::column/@dbcolumn)]">
     <xsl:variable name="p" select="position()"/>
     <xsl:variable name="l" select="last()"/>
     <xsl:variable name="dbcolumn" select="@dbcolumn"/>
     <xsl:for-each select="$dbdef">
        <xsl:if test="key('dbdef-cols', $dbcolumn)">
           <xsl:value-of select="$dbcolumn"/>
           <xsl:if test="$p &lt; $l">
              <xsl:text>, </xsl:text>
           </xsl:if>
        </xsl:if>
     </xsl:for-each>
  </xsl:for-each>

The output of this fragment might be:

select col1, col2, col3

This all works fine, except for one case - where the last column is
not found in the $dbdef file (where the 'if test=key' fails). Then I
get:

select col1, col2,

The position() < last() test doesn't work here. Can someone see a
better way to avoid that last comma?

Thanks,
John Sands

--


System Development
VIRBUS AG
Fon  +49(0)341-979-7419
Fax  +49(0)341-979-7409
joerg.heinicke@xxxxxxxxx
www.virbus.de


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