[dba-SQLServer] Combining Data from OLAP and OLTP

This is becoming an important issue for me. Assume an OLAP db that gathers
its data with a frequency of let's say once a day, and an OLTP db that
gathers its data very frequently, let's say 100 transactions an hour. I need
to combine them into a result set. While we're all asleep, the OLAP part can
roll up its aggregates etc., that's not complex. But I'm wondering about the
joins with the current data plus the history. I am not sure how this is
done. Never done it before, want to get it right. The OLAP part is simple:
dimension this and that and the other thing and you're done. But the current
data happens way too quickly to think about rolling it into the OLAP part
and then interrogating the cube. So how does one combine the cube with the
OLTP data? I've been reading this and that and so far have no clear-cut
answer on this.

Anybody been there and done that?

TIA,
Arthur