Denormalized tables within OLTP database
What you are thinking about is relatively common and pre-processing the data can indeed help the performance of reports and web pages.  The 'cost' to this is that the pre-processing takes time, so your denormalized tables (you can think of this as a  mini-OLAP Data Warehouse) are never fully up-to-date.

I do not consider that to be a big problem, but just one that your users need to understand.  (E.g. - "I just finished the xyz transaction and it is not in my report.")

Any reports that need the latest transaction will need to include at least some elements from the live data, instead of the pre-processed "OLAP" data.

Here is a generic link explaining the relationship. http://datawarehouse4u.info/OLTP-vs-OLAP.html

The web page also explains some nuances of the OLTP/OLAP divide, but there is nothing really surprising in the description.