ix_sel - Index selectivity 索引選擇率是Oracle中CBO 基于成本優化器重要的參考名額 ，反應了符合謂詞條件 通過索引主導列通路表上資料行的比例。(ix_sel - Index selectivity. Fraction of the table rows accessed by the indexes leading column in order to meet the predicate supplied. (10053)。
本文轉自maclean_007 51CTO部落格，原文連結:http://blog.51cto.com/maclean/1278540
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