Posted on September 12th, 2007

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Today’s post comes from a tutorial I’m working on for a customer who still does a lot of XML/XSL stuff. One of the more challenging things to do in XSL1.0 (which is what most browsers support) was getting a distinct list of values from a set of nodes. Exslt has a good article on the subject, including this link to Jeni Tenison’s XSLT Template. In the back of my mind, I kept wondering if there was some way to do this with keys, and the customer I’m working with showed a way they do it.

Let’s say you have an XML document like:

 

    FL
 

 

    GA
 

 

    MN
 

 

    FL
 

And you want to output something like:

  FL
  GA
  MN

The way to do this with keys is to define an xsl:key like this:

This let’s us set up a key to access Address nodes with. We can then get the distinct list in an xsl:for-each node by combining this with the generate-key function:

generate-id “generates a key that uniquely identifies a specified node“, in this case, basically creating a node-set of the state nodes and returning the first node for each distinct value. So our full xsl would look something like:

 

Which is all well and good. However, in the tutorial example, state isn’t in its own node – it’s embedded in the Address like:

123 Sample Way, Tampa, FL

Which is a tad trickier. In the tutorial, we’ve allowed the assumption that the state will always be the last 2 characters of the Address field. So how can we get a distinct list of states with data like this?

Turns out that we can do it in a very similar (if complex) way. We start off by specifying the key:

Here, our Address node is a child of Customer, which is a child of Customers – the root node. So we are matching Customers/Customer, and using the value of the last 2 characters of the Address. We then need to do the same for our for-each loop:

 
   
       name=”state”
       select=”substring(Address, (string-length(Address)-1))”/>
  

So we are doing the unique select on the state value. However, this returns the matching node – which is an Address node, so to use the value (in our example here as a parameter to a named template) we have to still substring it out.

Of course, this would probably be a better time to either see if you can get State into its own node, or do some sort of pre-processing to do that, but when you have neither of those options, this will work.

Thanks to Len and the SR team for the initial key idea

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6 Responses to “Getting a distinct list of values in XSL from a substring of data in a node”

1. Anonymous says:

   September 14, 2007 at 2:48 pm

   Or you could just put a bullet in your head.
2. Nicky says:

   December 5, 2007 at 2:22 am

   pls put ] at the end of xsl:for-each
   before closing xsl:for-each
   Else everything workig fine.
   Thanks a lot.
   Karishma
3. Anonymous says:

   November 20, 2008 at 4:45 am

   A whole year after this post, and the information is very helpful. Thanks very much.

   Carl.
4. Anonymous says:

   May 13, 2009 at 9:57 pm

   two years, still helpful
5. Joe Schmoe says:

   September 23, 2009 at 2:39 pm

   I agree with the first commenter. Seems like that would be much quicker and less painful.
6. San says:

   November 6, 2009 at 7:55 am

   I am looking for some thing on this lines, but the code lines are missing, can you please update it.

   Cheers,
   San