I have no specific experience on MSSQL import/export. But when you update tables on a database level you bypass all applicative controls. So if you update a subset of data you may create inconsistencies in the database and corrupt your database with no other choice but to restore the last uncorrupted backup. Due to the risk, I recommend to never do this on a production folder. If someone has a different experience to share, I would be very interested.

Agreed with Julien here, if this is the route you must take you can also see an alternative using BPC to export and import data. See below:

www.sagecity.com/.../how-to-reduce-time-taken-exporting-importing-folder-data-1916367834