If I understand what you've done correctly, you may need to set the value of F11_F_ACTIVIDAD in a onLoad computation, not as what I suspect is a default value?
It may also not like the to_date around the nvl.
To simplify your query, (among other methods) you may be interesting in using trunc. eg:
and trunc(h.f_actividad,'mm') = trunc(nvl(to_date(:F_actividad), sysdate),'mm')
You´re right......the page item :P11_F_ACTIVIDAD is configured with sysdate as default value and the original constrain was without the NVL:
AND substr(to_char(h.F_ACTIVIDAD,'DD MM YYYY'),4,7)=substr(to_char(to_date(:P11_F_ACTIVIDAD,'DD MM YYYY'),'DD MM YYYY'),4,7)
Now, in order to set the value of :P11_F_ACTIVIDAD in a onLoad computation.....you mean a "Calculation"?, where do I have to create the Onload Computation?....In page 1- Home or in page 12 (where item :P11_F_ACTIVIDAD and query exist)?.....Could you give me some tips to do this?
Thanks one mere time,
The reason you need a computation is to set session state, so when SQL is executed the database also knows what the browser knows (default value)
If you create a compution page component (below items, above process on the component view) and set the computation point to "Before header" - you won't need the default value