create or replace package pkg as
  cursor cur is
    select 1 n from dual;    
  type tcur is ref cursor return pkg.cur%rowtype;  
end pkg;
/

--类型报错
declare
  cur pkg.tcur;
begin
  open cur for 
    select ‘a‘ s, 1 n from dual; --跟游标定义的类型不一致
end;
/

--正常运行
declare
  cur pkg.tcur;
begin
  open cur for 
    select ‘kkk‘ n from dual;
end;
/

--正常运行
declare
  cur pkg.tcur;
begin
  open cur for 
    select 900 n from dual;
end;
/