The Oracle data block format is similar regardless of whether the data block contains table, index, or clustered data.
数据块的这部分包括了表和索引的数据。
This model has defined 4 extra persistent DOM node types, designed a storing method of mixed structure XML documents and created clustered data based on XML document orders.
此模型扩展定义了4种持久化dom节点类型，设计了一种存储混合型XML文档的方法，并依据文档的次序建立了数据聚集。
But, row level sampling may produce more accurate statistics if relational data values are highly clustered.
但是，如果关系数据值是高度聚集的，那么行级抽样可以产生更精确的统计信息。
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