与计数函数类似，当在一个规则中使用多个具有分组关键字的聚合，对分组与计数操作必须进行级联，如图14所示。
Like the counting function, when several aggregations with grouping keys are used in a rule, the group and count operations must be cascaded as shown in figure 14.
但是，如果使用具有相同分组关键字的多个聚合，或者对相同列进行计数的计数函数，其不会显著增加规则的执行时间。
But if you use multiple aggregations with the same grouping keys, or multiple counting functions that count the same column, it will not significantly increase the execution time of the rule.
影响任务复杂性的相关要素是不同分组关键字的数量，而不是在计数函数中所看到的，不同的所聚合列的数量。
The relevant factor that impacts the complexity of the job is the number of different grouping keys, not the number of different aggregated columns that you would see in counting functions.
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