alter table modify column ...

Hi!

I would like to know if there is anything similar to Informix-sql sintax to modify a column type.

I want to change a column from varchar(40) to varchar(40)[].

Do I have to make a stored procedure?
Is there any way to cast a varchar to a _varchar.

Something similar to:

create table kk4 as select numero, idproy, foto, '\'{"' || nombre::_varchar || '"}\'' as nombre, descrip from proy_foto;
ERROR: Cannot cast type 'varchar' to '_varchar'

Any idea will be appreciated.

Thanks in advance
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Evelio Martínez