比较表并查找不匹配计数的元素

Question

我有两张桌子

表1

表2

现在我想要那些RequestId和Table1中那些与Table2不同的RequestId的计数，例如，输出应该是

我可以通过以下查询从这两个表中获取单个计数和RequestId：

select RequestId, Count(RequestId) AS [Count] from Table1 group by RequestId

但是如何在一个查询中比较两个表，任何帮助都会很好，如果没有执行循环直到它执行它的唯一方法将是好的，因为这两个表中有很多记录，图像共享这里只是为了理解。

Answer 1

您将查询用作FROM中的子查询。外连接表2，因为其中包含所有请求ID的行：

select t1.requestid, t1.cnt - coalesce(t2.cnt, 0) as diff
from (select requestid, count(*) as cnt from table1 group by requestid) t1
left join (select requestid, count(*) as cnt from table2 group by requestid) t2
  on t2.requestid = t1.requestid
where (t1.cnt - coalesce(t2.cnt, 0)) > 0;

Answer 2

如果我没有弄错你，那么你可以使用你的查询来检查每个表中的RequestId的数量，然后通过计数加入它们甚至不是。并做简单的数学运算：

select t1.RequestId, (t1.Count - t2.Count) as count 
 from
 (select RequestId, Count(RequestId) AS [Count] from Table1 group by RequestId)t1
left join(select RequestId, Count(RequestId) AS [Count] from Table2 group by RequestId)t2
on t1.RequestId = t2.RequestId  
where t1.Count <> t2.Count