But the selectivity calculated in this way is not as accurate as selectivity calculated using data distribution.
但是，使用该方式计算的选择性不如使用数据分布计算的选择性准确。
However, in the absence of data distribution information, the optimizer will calculate selectivity for filters of different types based on table indexes.
然而在缺乏数据分布信息的情况下，优化器将基于表索引计算不同类型筛选器的选择性。
The optimizer USES data distribution information generated by UPDATE STATISTICS to calculate selectivity for the filters in the query.
优化器使用UPDATE STATISTICS所生成的数据分布信息来计算查询中筛选器的选择性。
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