Need Selected Date + 30 days data

Someone asked a question on a “Siebel Analytics” email group a few days ago that I thought was worth discussing briefly here. The question posed was how to put a date prompt on a dashboard and return data for that date and the next 30 days. The solution could not involve presentation or report variables, since these were introduced only in a later version of Siebel Analytics that the person who posed the question did not have.
When you have a problem like this, it usually helps to think about the SQL the BI Server would need to generate. In this case, it would include a WHERE clause with a BETWEEN predicate. That is, the normal key/foreign key equijoin between the fact table and the period table would have to become a join of the fact table  foreign key between a date in the period table and that date plus 30 days. This is a good example or a key principle: whenever a join condition needs to change, you should think about creating a new alias that uses that join condition.
Here’s an example of the usual equijoin of the period table (“TIME”) to the fact table (“TIMECOMPAREFACTS”).
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Using an alias of the fact table (“TimeSpanFacts”) and a“complex” instead of a physical foreign key join, the join expression changes.
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Now the user picks a date with the dashboard prompt and clicks Go.
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The BI Server generates the SQL needed as specified in the metadata.
select T463.DATE_ as C1
,Sum(T884.QS) as C2
,Sum(T884.DOLLARS) as C3
from TIME  T463
, TIMECOMPAREFACTS T884 /* TimeSpanFacts */
where
(
T463.DATE_ = To_date('2009-04-01','YYYY-MM-DD')
and
T884.DATEKEY between T463.DATE_ and (T463.DATE_ + 30) )
group by T463.DATE_
order by C1