As a matter of style I would recomend using the "as" consistently. It reads better.

BTW, "Regions as M"? Maybe there is a reason to use M for the Regions table, but I would expect R or (in case the table was used several times in the query) something like R_old, R_new, R1, R2, .... In either case I do not see why would you use an alias in a query that only includes one table. I guess a matter of style again :-)