Question

您能否根据要求建议如何显示以下数据。

表（XX）数据：

id  type amount
--- ---- -----
1    A     23.0
2    A     12.0
3    A     34.0
4    B     17.0
5    B     16.0
6    B     20.0

要求：我想显示如下输出

type A amount   type B amount
-------------   -------------
23.0             17.0
12.0             16.0
34.0             20.0

我尝试了以下查询，但它正在获取重复的行

select a.amount,b.amount 
from xx,(select * from xx where type='A')a,(select * from xx where type='B')b
where xx.id=a.id and xx.id=b.id

Answer 1

这是一种痛苦。您似乎希望将值作为“列表”放在每列中。这不是SQL方式，但它有可能：

select max(a.value) as a, max(b.value) as b
from (select xx.*, rownum as seqnum
      from xx
      where type = 'A'
     ) a full outer join
     (select xx.*, rownum as seqnum
      from xx
      where type = 'B'
     ) b
     on a.seqnum = b.seqnum
group by coalesce(a.seqnum, b.seqnum);

如果要保留原始排序，可以将order by id添加到子查询中。

编辑：

注意，另一种方法是使用union all：

select max(a) as a, max(b) as b
from ((select rownum as seqnum, value as a, NULL as b from xx where type = 'A'
      ) union all
      (select rownum as seqnum, NULL, value from xx where type = 'B'
      )
     ) ab
group by seqnum;

Answer 2

如果A的数量始终与B的数量相同，并且A总是第一个：

select ta.amount as "table A amount",
       tb.amount as "table B amount"
from tablename ta
  join tablename tb on ta.id + (select count(*) from tablename) / 2 = tb.id

SQL查询根据需要显示表数据

2 个答案: