I'm quite sure this works, only don't tell support!
Because directly altering the DB might lead you to data corruption, it is prohibited unless on behalf of support.
If you're not able to do it through the GUI or the BLCLI, then file an enhancement request in Soffront.
Yes, ALWAYS make sure you get the blessing from Support before modifying the database.
Is there an approved way of doing this? I need to change a "string" to a "string enumeration" value.
Contact support, but my experience has been no.