使用where子句计算列

Question

有没有办法计算Hive中每行具有特定值的列数。 我有数据看起来像输入，我想计算有多少列有价值＆＃39; a＆＃39;以及有多少列有价值＆＃39; b＆＃39;并获得输出＆＃39;输出＆＃39;。 有没有办法用Hive查询来完成这个？

Answer 1

Hive中的一种方法是：

select ( (case when cl_1 = 'a' then 1 else 0 end) +
         (case when cl_2 = 'a' then 1 else 0 end) +
         (case when cl_3 = 'a' then 1 else 0 end) +
         (case when cl_4 = 'a' then 1 else 0 end) +
         (case when cl_5 = 'a' then 1 else 0 end)
       ) as count_a,
       ( (case when cl_1 = 'b' then 1 else 0 end) +
         (case when cl_2 = 'b' then 1 else 0 end) +
         (case when cl_3 = 'b' then 1 else 0 end) +
         (case when cl_4 = 'b' then 1 else 0 end) +
         (case when cl_5 = 'b' then 1 else 0 end)
       ) as count_b
from t;

要获得总计数，我建议您使用子查询并添加count_a和count_b。

Answer 2

将lateral view与explode一起使用，并对其进行汇总。

select id
,sum(cast(col='a' as int)) as cnt_a
,sum(cast(col='b' as int)) as cnt_b
,sum(cast(col in ('a','b') as int)) as cnt_total
from tbl
lateral view explode(array(ci_1,ci_2,ci_3,ci_4,ci_5)) tbl as col
group by id