[請益] DB設計上為何不要都開NVARCHAR2(4000)
各位前輩,目前同仁們在討論一個問題,主要是關於資料庫設計方面,
根據Oracle的說明 NVARCHAR2 為長度可變動的欄位格式,
有個問題是,假設設計身分證的欄位,
當我把欄位設定成ID_NUM NVARCHAR2(10) 與 ID_NUM NVARCHAR2(4000)
就前提來看,只要我都只存10個字元,那個所占用的空間"應該"是一樣的,
如果說站在這個角度上,我將所有的欄位都設定成 NVARCHAR2(4000),
那麼有沒有非常顯在的缺點 ?
目前是想像的到的
1. 無法從DB Schema看出長度限制
2. table fragmentation
3. 效能問題
還有其他潛在的問題嗎 ? 若是都把欄位設成NVARCHAR2(4000)的話呢 ?
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