How to change the data type of column in oracle

Question

I have a master table.It contains 1300000 records.I want to change a column type from VARCHAR(100 CHAR) to VARCHAR2(300 CHAR).

I planned a way to do this. I will create a new column with a new name then I will copy data from old column to new column then I will drop old column and rename new column with old column name.

But master table contains a trigger. It adds data to master_history table for update and delete processes. So, how will the trigger affect my way? If I do process above , Is it okey?

My trigger is :

ALTER TRIGGER "TRG_MASTER_" ENABLE;
CREATE OR REPLACE TRIGGER "MASTER" AFTER
    UPDATE OR
    DELETE ON MASTER FOR EACH ROW 
BEGIN
    INSERT
    INTO MASTER_HISTORY
       (
       ORDER_ID,
       CUSTOMER_FIRST_NAME,
       CUSTOMER_LAST_NAME,
       CUSTOMER_EMAIL,
       CUSTOMER_ADRESS      
       )
    VALUES
       (
       :OLD.ORDER_ID,   
       :OLD.CUSTOMER_FIRST_NAME,
       :OLD.CUSTOMER_LAST_NAME,
       :OLD.CUSTOMER_EMAIL,
       :OLD.CUSTOMER_ADDRESS,           
       );
END;

Answer 1

As far as concerns, there is no need for this complex logic. Oracle lets you extend the width of a varchar column with the following command:

ALTER TABLE master_history MODIFY mycol VARCHAR2(300);
                               --^-- modify this to your real column name

Extending the width of the column does not affect existing data.