It is highly recommended not to store any CC numbers in a database, unless you absolutely have to and you ahve the highest level of security applied to the server and database files as well. In most cases, where CC numbers are stored for user convenience, they store the entire number, minus the last 4 digits, so that the entire number isnt stored, but users only have to type in the last 4 digits when they visit the site again in the future.
Ask yourself if you absolutely have to store these CC numbers.......