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问答- 问题:postgres：获取每个组中前n个出现的值

postgres：获取每个组中前n个出现的值

postgres：获取每个组中前n个出现的值

with cte as (
    select 
        t.user_id, t.letter,
        row_number() over(partition by t.user_id order by count(*) desc) as row_num
    from Table1 as t
    group by t.user_id, t.letter
)
select
    c.user_id,
    max(case when c.row_num = 1 then c.letter end) as "1st-most-occurance",
    max(case when c.row_num = 2 then c.letter end) as "2st-most-occurance"
from cte as c
where c.row_num <= 2
group by c.user_id

Postgres 2022/1/1 18:35:56 有340人围观

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