declare
    column_exists exception;
    pragma exception_init (column_exists , -01430);
begin
    execute immediate 'ALTER TABLE FISCAL_IMPRESSORA ADD (INDGERAARQGT NUMBER(1))';
    exception when column_exists then null;
end;
/
declare
  ja_existe  exception;
  pragma exception_init (ja_existe  , -00001);
begin
  execute immediate 'UPDATE FISCAL_IMPRESSORA SET INDGERAARQGT = INDCTRL';
  exception when ja_existe  then null;
end;