[Zope] ZSQL: how to definde null

[Dieter Maurer]

Christoph Landwehr wrote at 2003-10-27 14:13 +0100:
 > Dieter Maurer schrieb:
 > 
 > > Christoph Landwehr wrote at 2003-10-21 00:57 +0200:
 > >  > I have a ZSQL method, that looks like
 > >  > 
 > >  > Attributes:
 > >  >   some_name='empty'
 > >  > 
 > >  > UPDATE
 > >  >     foo
 > >  > SET
 > >  >     bar = <dtml-sqlvar some_name  type="string">
 > >  > WHERE
 > >  >    some contitions ... ;
 > > 
 > > You can try the "optional" attribute for "dtml-sqlvar".
 > > You might need to use "type=nb" (non blank) rather than "type=string".
 > 
 > In this case I dont't see how this could work, because I have to define 
 > 'some_name' in the SQL-Method's Attributes and supply a default value in 
 > case the user does not supply a value for 'some _name' in the form that 
 > feeds the SQL-Method. Therefor sone_name is never blank and the optional 
 > never is true.
 > 
 > Am I missing something?

Yes, you should read the documentation for "dtml-sqlvar" and its
attribute "optional":

      optional -- A flag indicating that a value is optional.  If a
                  value is optional and is not provided (or is blank
                  when a non-blank value is expected), then the string
                  'null' is inserted.

Thus, you would use "type=nb" and ensure that the value is blank
(empty) iff you want to render "null".

-- 
Dieter