优化器根据可用的统计信息计算基数的估计值，即预计查询返回的行数。
The optimizer calculates its cardinality estimate — that is, the estimated number of rows returned by the query — based on the statistics available.
此估计值可用于安排资本需求。
This estimate can be used to set capital reserve requirements.
此估计值可用于安排资本需求。
This estimate can be used to set capital reserve requirements.
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