Use alter table to encrypt or decrypt existing data or to add an encrypted column to a table.
Encrypt a column:
alter table tablename add column_name encrypt [with [database.[owner].]keyname
Decrypt an existing column:
[decrypt [with [database.[owner].]keyname]]
keyname – identifies a key created using create encryption key. The creator of the table must have select permission on keyname. If keyname is not supplied, Adaptive Server looks for a default key created using create encryption key or alter encryption key as default.
Create an encryption key and encrypt ssn column in existing “employee” table.
alter table employee modify ssn encrypt with ssn_key grant decrypt on employee(ssn) to hr_manager_role, hr_director_role
Use alter table to change an encryption key. When the encrypt qualifier is used on a column that is already encrypted, Adaptive Server decrypts the column and re-encrypts it with the new key. This operation may take a significant amount of time if the table contains a large number of rows.
