ALTER TABLE tablename SET UNUSED (COLUMN columnname | (col1, col2, ...) ) [CASCADE CONSTRAINTS | INVALIDATE]; ALTER TABLE tablename DROP (COLUMN columnname | (col1, col2, ...) | UNUSUED COLUMNS) [CASCADE CONSTRAINTS |INVALIDATE]; ALTER TABLE STORM_TRACK SET UNUSED (LAT,LON); ALTER TABLE STORM_TRACK DROP UNUSED COLUMNS; ALTER TABLE SHIPPING ACTION DROP COLUMN LOG_TIME;
SET UNUSED | After setting a column as unused, it does not appear in the DESC command, or in SELECT * queries. |
[CASCADE CONSTRAINTS | INVALIDATE] | CASCADE CONSTRAINTS must be used if a constraint contains a combination of used and unused columns. |
INVALIDATE | INVALIDATE causes Oracle to invalidate objects that depend on the dropped or unused column(s), such as views. Currently, this is always done, whether or not you specify the
INVALIDATE keyword. |