If more than one column is aggregated using the same grouping key or without a grouping key, then all the aggregations are computed within the same operation with a single pass over the data.
如果利用相同的分组关键字或者没有分组关键字，来聚合多个列，那么，所有的聚合都在单个数据传递中的相同操作中进行。
Selection of part of a wave on account of time or magnitude. Operation of a circuit when one wave allows another to pass during specific intervals.
根据时间或幅度选择波形的一部分，即在一个特定的间隔里一个波形允许另一个波形通过电路的动作。
The Third Party Logistics is one kind of advanced organization pattern of Logistics, To realize the value of Logistics must pass the operation of the corporation of Logistics.
第三方物流是一种先进的物流组织模式，其创造和实现价值必须依赖于物流企业的微观运营。
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