[Koha] SQL field lengths

[Paul]

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