Modify a column data type or size in Oracle

Modifying a column data type or size in Oracle is done by using the constructs below

1. Changing the column data type:
   ALTER TABLE <Table name>
   MODIFY ( <Column Name> <New data type>)
   
2. Changing the size of a column:
   (Assuming the previous data type of column was varchar2 with the length of 20 and it needs to be changed to 10)
   ALTER TABLE <Table name>
   MODIFY ( <Column Name> VARCHAR2(10))
   

Note: Text within <> indicate the parameters that need to be replaced.