Question

我有两个表：

table_1:  
A | B | C  
z | x | 12  
z | c | 13  
z | c | 10  
a | s | 14  
a | d | 11  

table_2:  
A | B | C  
z | c | 10  
z | x | 15  
z | x | 11  
a | d | 14  
a | s | 12

我要：
-按A和B将表分组
-并找出AB的C的总和的差异。

我从开始：

SELECT A, B, SUM(C) from table_1 GROUP BY A, B;  
SELECT A, B, SUM(C) from table_2 GROUP BY A, B;

但是我不知道如何通过添加相等的附加列来加入它们到table_1.sum（C）-table_2.sum（c）

预期结果如下：

A | B | sum1 | sum2 | diff  
z | x | 12   | 26   | -14 
z | c | 23   | 10   | 13
a | s | 14   | 12   | 2
a | d | 11   | 14   | -3

Answer 1

与子查询一起使用连接

select X.A,X.B, sum1, sum2, sum1-sum2 as diff from 
(
SELECT A, B, SUM(C) sum1
from table_1 GROUP BY A, B  
)X inner join
(
SELECT A, B, SUM(C) sum2
from table_2 GROUP BY A, B
)Y on X.A=Y.A and X.B=Y.B

Answer 2

当两个表中的组不同时，您想做什么？ inner join可能很危险，因为群组会消失。

如果要保留所有组，则一种方法是union all / group by：

select a, b, sum(c1) as sum1, sum(c2) as sum2,
       (sum(c2) - sum(c1)) as diff
from ((select a, b, c as c1, 0 as c2
       from table_1
      ) union all
      (select a, b, 0 as c1, c as c2
       from table_2
      )
     ) t
group by a, b

从两个选择中找到结果的差异

2 个答案: