Hive面試題：multi group by的好處，舉例說明

multi group by 能夠將查詢中的多個group by操做組裝到一個MapReduce任務中，起到優化做用優化 例子：ci select Provice,city,county,count(rainfall) from area where data="2018-09-02" group by provice,city,countit select Provice,count(rainf

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