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[SQL] PRIMARY KEY 與 CLUSTERED INDEX 差別與使用時機(資料倉儲設計筆記)
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[SQL] PRIMARY KEY 與 CLUSTERED INDEX 差別與使用時機(資料倉儲設計筆記)

SQL Server 中,PRIMARY KEY 與CLUSTERED INDEX 常常被混淆。很多人在學 SQL 時會問:PRIMARY KEY 一定是 CLUSTERED INDEX 嗎?兩者差在哪裡?在資料倉儲中應該怎麼使用?這篇文章會用簡單方式整理兩者差異與實務應用,如果沒有 Index,執行SQL時,資料庫會逐筆掃描整張表,這叫做:Table Scan,如果建立 Index,資料庫可以直接找到資料位置,查詢速度會快很多