SELECT CATEGORY,TYPE FROM (

SELECT DISTINCT CATEGORY, TYPE FROM XXX WHERE ooo=zzz

UNION

SELECT 'SQL' AS CATEGORY, A.TYPE FROM OOO WHERE qqq=eee

...

)

ORDER BY LOWER(1), LOWER(2)

如果 UNION 的欄位型態不一致, 就會發生 {ORA-12704:字元設定不符合} 這個錯誤, 解決方法就是將型態轉為一致, ex :

SELECT 'SQL' AS CATEGORY

改為

cast('SQL' as nvarchar2(5)) AS CATEGORY