creating historical reports independent of individual column data

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While creating a report that relies on more than one date column (incidents.created and incidents.closed) to calculate backlog, it didn't appear possible to perform a straightforward query.  In order to work around this problem, I created multiple columns with date offsets. 

 

For example,  in order to calculate backlog for each day of the week, I resorted to multiple columns where each column is offset by a given number of days from a starting date $date_param:

 

sum(if(incidents.created < date_add(date_trunc($date_param, IWEEKS), 1, DAYS, 1) & nvl(incidents.closed, sysdate()) >= date_add(date_trunc($date_param