Change view definition - do not have to drop it

Original view1 (col1 bpchar, col2 varchar).

Now I need update view1 definition to
create or replace view view1 as select col1, col2 from new_table;

However, col1 in new_table is not bpchar. This gives me headache! There
are tens of dependent views based on view1, so I cannot just drop view1
and recreate it.

How I can redefine view1 without dropping it and recreate it?

Thanks a lot!

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Lu Ying