oracle - PL/SQL：将数据类型分配给变量

Question

有没有办法做到这一点？我希望这样做：

create or replace
package SOME_PACKAGE as
  filetype type is clob%type; --assign clob's filetype to a variable
end SOME_PACKAGE;
/

declare
  clb SOME_PACKAGE.filetype;
begin
  dbms_lob.writeappend(clb, 1, 's');
end;

谢谢！

Answer 1

你可以这样做：

create or replace
package SOME_PACKAGE as
  subtype filetype is clob; --assign clob's filetype to a variable
end SOME_PACKAGE;
/

但为什么 ？？