同时从每一列中获取每个值的计数

Question

我试图看到类似的问题，但 none 正在以有效的方式帮助解决这个问题。

我有一个 table 列，如下所示：

我想计算每一列中值的出现次数，但对于 table 的所有列，而不是只有一个。

我想得到这样的东西：

p7     |  p7_count | p9 | p9_count
B      |   1       | A  |  2
A      |   1       | E  |  1
C      |   1

但我只能对每个查询使用一个查询来获取它，例如：

SELECT p9, count(*) AS p9_Count
FROM respostas 
GROUP by p9
ORDER BY p9_Count DESC

但是我得到的结果是：

有没有一种方法可以对所有列执行此操作，而不必分别对每个列执行此操作并分别获得结果？

Answer 1

您可以使用 union all 来执行此操作。有点不清楚你到底想要什么。也许这很接近：

select p, max(p7cnt) as p7cnt, max(p8cnt) as p8cnt, max(p9cnt) as p9cnt
from ((select p7 as p, count(*) as p7cnt, 0 as p8cnt, 0 as p9cnt
       from respostas
       group by p7
      ) union all
      (select p8, 0 as p7cnt, count(*) as p8cnt, 0 as p9cnt
       from respostas
       group by p8
      ) union all
      (select p9, 0 as p7cnt, 0 as p8cnt, count(*) as p9cnt
       from respostas
       group by p9
      )
     ) ppp
group by p;

Answer 2

我认为这就是您想象的那种事情。它变得有点混乱，但您可以通过添加到合并来扩展它。为了让它与 row_number 函数一起工作（对于 MySQL），我将其转换为使用子查询。当行数变大时，这甚至不会有效，因为 SQL 不是这项工作的正确工具。

select
    p1, p1_count, p2, p2_count, p3, p3_count
from
(
    select
        p1, p1_count,
        (
            select count(*) from
                (SELECT p1, count(*) AS p1_Count FROM respostas GROUP by p1) as t2
            where
                    t2.p1_Count <= t1.p1_Count
                or (t2.p1_Count  = t1.p1_Count and t2.p1 <= t1.p1)
        ) as rownum
    from (SELECT p1, count(*) AS p1_Count FROM respostas GROUP by p1) as t1
) as tt1

    full outer join

(
    select
        p2, p2_count,
        (
            select count(*) from
                (SELECT p2, count(*) AS p2_Count FROM respostas GROUP by p2) as t2
            where
                    t2.p2_Count <= t1.p2_Count
                or (t2.p2_Count  = t1.p2_Count and t2.p2 <= t1.p2)
        ) as rownum
    from (SELECT p2, count(*) AS p2_Count FROM respostas GROUP by p2) as t2
) as tt2
    on tt2.rownum = tt1.rownum

    full outer join

(
    select
        p3, p3_count,
        (
            select count(*) from
                (SELECT p3, count(*) AS p3_Count FROM respostas GROUP by p3) as t2
            where
                    t2.p3_Count <= t1.p3_Count
                or (t2.p3_Count  = t1.p3_Count and t2.p3 <= t1.p3)
        ) rownum
    from (SELECT p3, count(*) AS p3_Count FROM respostas GROUP by p2) as t3
) as tt3
    on tt3.rownum = coalesce(tt1.rownum, tt2.rownum)

order by
    coalesce(tt1.rownum, tt2.rownum, tt3.rownum)

同时从每一列中获取每个值的计数

Get a count of each value from every column at the same time

mysql

sql

select

group-by

count