Oracle SQL: Unused Columns & Virtual Columns

Oracle SQL utilizes SET UNUSED for logical deletion, hiding column metadata without rewriting data blocks to avoid heavy I/O and locks. This instant operation prevents production delays. Additionally, Oracle provides pseudo-columns, which function like table columns but are not stored on disk. While users can SELECT from pseudo-columns such as ROWID, ROWNUM, NEXTVAL, and CURRVAL, they cannot perform INSERT, UPDATE, or DELETE operations on these values, as they serve specific administrative and navigational purposes.