SQL JOIN或UNION还是什么？

Question

我有3个名为A，B和C的表。表A有a列。表B列a，b。表C列a，c。这些表包含如下数据：

我想从A，B，C获取所有数据，其中a = 1

我想要的输出应如下所示：

但我从SSMS获得的结果如下：

我应该如何重构SQL以获得所需的输出？

e.g。我不希望列中的重复值

Answer 1

您需要加入这些值，但不仅要加在a值，还要加在位置上。 SQL表表示无序集。我将假设b和c列代表排序。

select a.a, b.b, c.c
from (select a.*, row_number() over (order by a) as seqnum
      from a
     ) a full outer join
     (select b.*, row_number() over (partition by a order by b) as seqnum
      from b
     ) b
     on a.a = b.a and a.seqnum = b.seqnum full outer join
     (select c.*, row_number() over (partition by a order by c) as seqnum
      from c
     ) c
     on c.a = coalesce(a.a, b.a) and c.seqnum = coalesce(a.seqnum, b.seqnum)
where coalesce(a.a, b.a, c.a) = 1;