hive mapreduce中的计数计数

Question

我在hive中有一个表，包含

questionid,questiontag,answerID,userIDofanswerer 

我需要这个数据集中最常用的10个标签。

I tried:

select count(questionID),questiontag from table GROUP BY tags;

但是如何按Count(questionID)

Answer 1

在下面的查询中，ORDER BY cnt DESC LIMIT 10将选择最常用的10个标签:

    SELECT count(questionID) cnt ,
           questiontag 
      FROM table 
  GROUP BY questiontag 
  ORDER BY cnt DESC 
  LIMIT 10;

count(*)将计算包含NULL的所有行

count(questionID)将只计算questionID不为NULL的行

Answer 2

try below

select count(questionID) as cnt,questiontag from table GROUP BY questiontag
order by cnt desc limit 10;