[Zope3-dev] Re: [Zope-DB] Relational Databases in Zope 2 and
charlie at egenix.com
Tue Jun 29 05:54:26 EDT 2004
On 2004-06-29 at 10:22:14 [+0200], "Smith, Neil (Worcester)"
<Neil.Smith at npower.com> wrote:
> The point of the dtml-sqlgroup and dtml-sqltest is surely to provide a nice
> way of handling the case where you don't pass in the parameter, so it
> doesn't render the WHERE, AND, = etc. And it does this quite well.
Maybe it does. I've never found cause to use it and scratched my head a lot
trying to look at it. I'd hate to maintain such stuff something which Ian
Bicking seems to complain about.
> If you remove it, then you'll need either an exponential number of SQL
> methods and some logic before it to decide which to call, or you'll have to
> fill the SQL method with even more confusing dtml-if statements, or you'll
> have to have your SQL something like:
> WHERE (
> <dtml-sqlvar parameter_1 type=..> is null or
> column_1 = <dtml-sqlvar parameter_1 type=..>
> ) and (
> <dtml-sqlvar parameter_2 type=..> is null or
> column_2 = <dtml-sqlvar parameter_2 type=..>
Interesting example. This says to me that the model is bad: NULLs are
indicative of this. It's also intriguing that to see the relation variables
passed in as relation values. I think this will probably cause an error on
rendering. Okay, so nit-picking aside: you are right to say that <dtml-if>s
can cause problems on larger methods. I find that readibility is still there
but I get problems when I might only want to return a certain value based on
something I'm passing in. Working on my larger ZSQL methods has reminded me
of working on HTML pages which is why I find ZPT attractive.
I think what might be the biggest problem is the lack of good examples on
this. The stuff in Zope book does not seem to me to be written with real
world experience so maybe you've got a concrete example with the resultant
SQL for us to discuss?
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