Question

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有没有办法使用mysql将表聚合到这个？

+-----------------+------------+---
|  A          | B          | C    |
+-----------------+------------+---
|  a1         | NULL       | NULL |
|  a2         | NULL       | NULL |
|  NULL       | b1         | NULL |
|  NULL       | b2         | NULL |
|  NULL       | b3         | NULL |
|  NULL       | NULL       | c1   |
+-----------------+------------+---

但是，行数取决于列中非空值，其中具有最大数量的非空值，其余列将跟随。是否有查询来制作这样的东西？ PS：这是通过旋转文本值。

Answer 1

这不是一个支点。您正在尝试将事物列表放入列中。这不是一件非常SQL好的事情，但您可以使用变量（或MySQL 8 +中的row_number()）来完成它：

select rn, max(a) as a, max(b) as b, max(c) as c
from ((select (@rna := @rna + 1) as rn, a, null as b, null as c
       from t cross join
            (select @rna := 0) params
       where a is not null
      ) union all
      (select (@rnb := @rnb + 1) as rn, null, b, null
       from t cross join
            (select @rnb := 0) params
       where b is not null
      ) union all
      (select (@rnc := @rnc + 1) as rn, null, null, c
       from t cross join
            (select @rnc := 0) params
       where c is not null
      )
     ) t
group by rn
order by rn;

基于值的数据透视表和聚合

1 个答案: