Check out example codes for "orcale sql change column type". It will help you in understanding the concepts better.

Code Example 1

ALTER TABLE table_name

MODIFY column_name datatype;

Code Example 2

ALTER TABLE table_name 
MODIFY column_name action;

Code Example 3

ALTER TABLE table_name

ALTER COLUMN column_name datatype;

Code Example 4

ALTER TABLE table_name
ALTER COLUMN column_name datatype;

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