oracle中判斷欄位是否存在和新增表結構

declare cnt number;
begin
---查詢要建立的表是否存在
select count(1)
into cnt
from cols
where table_name = upper('sys_CustomReport')
and column_name = upper('FConfig');

---如果存在則刪除該表
if cnt<1 then
   execute immediate 'ALTER TABLE sys_CustomReport ADD FConfig Blob';
end if;
end;