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Hiveのcount()で空文字やnullはカウントされるか

hive

Posted at 2021-06-16

with t1 as (
  select 'A' as col1
  union all
  select 'B' as col1
  union all
  select ''  as col1
)
select count(distinct col1) from t1 -- 結果は3 (すなわち空文字はカウントされる！distinctを外しても同じ)

with t1 as (
  select 'A'  as col1
  union all
  select 'B'  as col1
  union all
  select null as col1
)
select count(distinct col1) from t1 -- 結果は2 (すなわちnullはカウントされない！distinctを外しても同じ)

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