第三个命令抽取 15% 的行，但是不收集分布统计信息，并对索引也应用了抽样，这不同于第一个命令和第二个命令。
The third command samples 15% of all rows, does not collect distribution statistics, and also applies sampling to indexes which the first and second commands didn't.
观察其模式，第2行使用第一个元素，第6行使用第二个该元素，第10行使用第三个该元素。
Looking for a pattern, row 2 USES the first element, row 6 USES the second, and row 10 USES the third.
每隔一行显示一个竞争者，即，第1行拥有序列中的第一个seed，第3行拥有序列中的第二个seed，第5行拥有序列中的第三个seed，等等依此类推。
A competitor appears in every other row, which means row 1 has the first seed in the sequence, row 3 has the second seed in the sequence, row 5 has the third seed in the sequence, and so on.
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