hive中count(distinct)的相关优化_hive count distinct优化-CSDN博客

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文章浏览阅读4.2k次，点赞2次，收藏22次。1、单个count(distinct)例子：select count(distinct id) as num from table_name方法1（简单，但很多时候效果不明显）select count(id) as num from (select id from table_name group by id) a;方法2（对分组字段进行加盐操作）select sum(tag_num) as numfrom (select tag ,cou_hive count distinct优化

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