[Koha] SQL field lengths

Problem: the CCODE in the Koha SQL database is limited to 10 characters only. We have (transferring our data from spreadsheets) dozens of categories that exceed this limit e.g. "marine biology", "yacht cruising", etc. Does anyone know of a quick way to modify the field length in SQL "on the fly"? Many thanks - the alternative is to manually correct tens of thousands of entries spread across hundreds of spreadsheets. Paul