估计行数_有道手机词典

1.查询优化器根据从每个表检索的行数估计查询成本。
The query optimizer bases query-cost estimates on the number of rows to be retrieved from each table.
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2.生成访问计划，查看优化器对该查询返回的总基数(行数)的估计值。
Generate the access plan and see what the optimizer estimates the total cardinality (Number of rows) returned by the query will be.
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3.此外，现在可以正确地估计结果集中的总行数。
Besides, the total number or rows in the result set is now estimated correctly.
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