I'm confused as to why you think it's not something that should be done within SQL. It's a non-indexed field that has no link to any other table and is merely a reference field which needs to be updated in order to optimize the cross over with over systems (Not linked).
The Update query is just for this sort of thing is it not?
This is the base of the update query that we have in place;
SET JOB_NUMBER = ORG_UNIT + " - " + " ??? - " + RIGHT(10000000 + JOB_NUMBER,6)
WHERE ORG_UNIT = 'ADXX'
AND ISNUMERIC(JOB_NUMBER) = 1