How to create a "Top N" report?

[jleyser]

 I'm an experience Crystal Reports user, now learning iReports.

Using grouping a sorting, I can print a 'rank' for each group, such as showing revenue per customer, using Grouping and the Group Footer Band.  Works great.  And, since it's part of the data source, I can sort the list on Customer Name.  So far, so good.

But what I really want to do is sort on the 'rank', which is being computed at report time.  So, instead of this:

customer-1 $1,000 total sales

customer-2 $2,500 total sales

customer-3 $1,500 total sales

I want:

customer-2 $2,500 total sales

customer-3 $1,500 total sales

customer-1 $1,000 total sales

Is that possible?  If so, how?

[slow]

I think that a variable computed for each row coming from db can't be used to order the final result set...

this because it seems to be a big cicle fetching the dataset... so if this variable is computed at time the data was retrieved, then the previous data are already computed

maybe you can emulate this variable at DB level when you select the data... passing it a s a field, and using it to order the data.