连接两个结构相似的表

Question

我有2种相同类型的表：T1和T2，具有4列（日期，标志，状态，计数）。我想计算表中计数的差异。我正在使用以下查询

`Select 
T1.date,
T1.flag,
T1.status,
T1.counts,
T2.counts
(T1.count-T2counts)as difference 
From T1
Left join T2
On T1.date=T2.date
And T1.flag=T2.flag
And T1.status=T2.status
`

，但无法获得所需的输出。任何建议将不胜感激。 样本数据和所需的输出如下

Answer 1

您可以使用union all和group by总结每个表中的内容：

select Date, flag, status, sum(count1) as count1, sum(count2) as count2,
       ( sum(count1) - sum(count2) ) as diff
from ((select Date, flag, status, counts as count1, 0 as count2 from table1) union all
      (select Date, flag, status, 0, counts as count2 from table1)
     ) tt
group by Date, flag, status;

Answer 2

您的查询中有几次错字。我对其进行了修改并添加了WITH语句，以便可以使用示例数据。结果看起来不错。

with T1 (mydate, flag, status, counts) as (select trunc(sysdate), 'Cat1', 1, '100' 
from dual), 
    T2 (mydate, flag, status, counts) as (select trunc(sysdate), 'Cat1', 1, '50' 
from dual)
Select 
T1.mydate,
T1.flag,
T1.status,
T1.counts T1Count,
T2.counts T2Count,
(T1.counts-T2.counts)as difference 
From T1
left join T2
On T1.mydate=T2.mydate
And T1.flag=T2.flag
And T1.status=T2.status