I want to get the last call_activity record for a single user. Is there ANY way to efficiently retrieve the last record for a specified user_id, or do I need to de-normalize and update a table with a single row for each user each time a new call_activity record is inserted? I know I how to do the query without the summary table (subquery or GROUP BY with MAX) but that seems like it will never perform well for large data sets. Or am I full of beans and it should perform just fine for a huge data set as long as I have an index on "called"?
