It is used to calculate the encryption and decryption columns and it is the logical identifier of the column in SQL. Logical columns contain ciphertext columns (mandatory), query-helper columns (optional), and plaintext columns (optional).
Encrypted data columns.
It is a helper column used for queries. For some non-idempotent encryption algorithms with higher security levels, irreversible idempotent columns are provided for queries.
The column is used to store plaintext and provide services during the migration of encrypted data. It can be deleted after the data cleansing is complete.