[系統] Oracle決定使不使用INDEX
大家好 小弟今天遇到一個非常奇怪的情況
我建立一個新的TABLE 欄位只有一個ID
把rownum放進ID INSERT 五百萬筆資料
也就是TABLE內有ID 1~ ID 5000000
再建立一個INDEX ON ID
接著測試 SELECT ID FROM TABLE WHERE ID=435323
發現執行計劃居然是FULL TABLE SCAN
此時再建立UNIQUE INDEX ON ID
再下一次剛剛的SQL發現執行計劃就走UNIQUE INDEX了
因為這是新的TABLE應該不會有需要analyze的問題..
我覺得這是一個非常基本的情況..不知為何沒使用INDEX?
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