I think you need to add 'ORDER BY MR_M ASC' in your sql statement. This tells the DB to return the data in a certain order.
I think if you put the same queries (SELECT MR_M FROM MR2 & SELECT MR_R FROM MR2) you would see that the database returns different values than 'select * from MR2 limit 10'
Also, you could select both columns in one query. I don't really see any reason not to, maybe you have one.