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Alter Table Tablename and Drop Columns

Drop columns 
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.
INVALIDATEINVALIDATE 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.