Answer Posted / nithya

To change the name of the column:

ALTER TABLE TABLENAME RENAME COLUMN OLD_COLUMN_NAME TO
NEW_COLUMN_NAME;

eg: alter table employee rename column emp_name to ename;

To change the datatype of a column:

ALTER TABLE TABLENAME MODIGY COLUMN_NAME NEW_DATA_TYPE;

eg: alter table employee modify ename varchar(50);

NOTE: u cannot modify column of a datatype from larger value
to smaller value.U can do it only if there is no data in ur
column.

eg: alter table employ_detail modify emp_addr varchar(5);

ORA-01441: cannot decrease column length because some value
is too big

alter table employ_detail modify emp_id number(2)

ORA-01440: column to be modified must be empty to decrease
precision or scale

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