oracle开窗函数,提高大数据量数据的检索速度，分类汇总和排序方便-oracle window function

物理结构：oracle物理文件的分类，8类数据文件，及其它们的作用与用途和被破坏时的恢复-oracle physical structure: the classification of the Oracle physical files, 8 data files, and their role and purpose and is destroyed when the recovery