[Zope] A conditional dtml-in tag?

[RI Dunfey]

Hi-

I have a dtml page which displays the results of a sql query:

<dtml-in expr="my_query(category1=category1, category2=category2)">
<TR><TD>
<dtml-var NAME>
</TR></TD>
</dtml-in> 

The values that are passed to the query are obtained from the request object.  
If the value for category2=None then I want to leave category2 out of the sql 
query as below:

<dtml-in expr="my_query(category1=category1)">
<TR><TD>
<dtml-var NAME>
</TR></TD>
</dtml-in>

The sql query has been designed to handle this using the optional tag.

However, it falls over if I break the in tags up with an if tag, e.g.:

<dtml-if "category2=None">
<dtml-in expr="my_query(category1=category1)">
<dtml-else>
<dtml-in expr="my_query(category1=category1, category2=category2)">
</dtml-if>
<TR><TD>
<dtml-var NAME>
</TR></TD>
</dtml-in>


I have also tried passing a string to the in tag, e.g.:

<dtml-if "category2=None">
<dtml-var dummystr="my_query(category1=category1)">
<dtml-else>
<dtml-var dummystr="my_query(category1=category1, category2=category2)">
</dtml-if>
<dtml-in expr=<dtml-var dummystr>>
<TR><TD>
<dtml-var NAME>
</TR></TD>
</dtml-in>

but the in tag cannot except a string?  I have also tried handling this in 
python, as it is logic, however this too has been unsuccessful and would quite 
allow me to format the results as desired.  I just want to control how the sql 
query is executed?  Depending on the value of variables in the request object.

Any help, much appreciated,

Rob