Should I use one or two tables for summary data?

[Quoted] I need to store data grouped by days and by producers and also summary data, that is the result of SUM() (for all producers) grouped by days.

Should I make two tables (one for producers data and one for summary one) or one table with `ProducerID IS NULL` indicating the summary data (sum for all producers)?

Don't advise not to store the summary data and use SUM() instead, because I want it to be fast in retrieval.

[Quoted] The data is also grouped by other fields.

-- 
Victor Porton - http://portonvictor.org