Question

我有以下现有表格（简化版本），我必须从中创建结果表格。我知道我必须做一些复杂的自联接才能到达结果表，但是无法让它工作。我唯一的另一种选择是编写程序或PL / SQL程序，如果可能的话我想避免这种程序。

PId     From    To      Timestamp field  
1       1       2       8/09/2014  
2       1       2       8/09/2014  
3       1       3       8/09/2014  
4       1       3       8/09/2014  
5       1       3       8/09/2014  
6       2       3       8/09/2014  
7       2       3       8/09/2014  
8       2       4       8/09/2014  
9       2       4       8/09/2014  
10      3       1       8/09/2014  
11      1       3       8/08/2014  
12      2       3       8/08/2014  
13      2       3       8/08/2014  
14      3       2       8/08/2014

要求是在前向（Outgoing）和反向（Incoming）方向上计算具有From-To组合的行数。将以查询的形式大大欣赏解决方案。请注意，最后2列还包括我在paranthesis中的注释，在预期值旁边。这是为了更好地理解需求。

结果表：

DaysOld     A       B       Outgoing(Comments)  Incoming (Comments)
1           1       2       2(PId: 1,2)         0
1           2       1       0                   2(PId: 1,2)
1           1       3       3(PId: 3,4,5)       1(PId: 10)
1           3       1       1(PId: 10)          3(PId: 3,4,5)
1           2       3       2                   0   
1           3       2       0                   2
1           2       4       2                   0
1           4       2       0                   2
2           1       3       1                   0
2           3       1       0                   1
2           2       3       2                   1
2           3       2       1                   2

Answer 1

除非它不包含冗余行，否则应该执行您之后的操作。可以通过与最大和最小的查询进行联合来添加它们。

SELECT LEAST(From,To) AS A, GREATEST(From,To) AS B, 
SUM(CASE WHEN FROM < TO THEN 1 ELSE 0 END) AS Outgoing
SUM(CASE WHEN FROM > TO THEN 1 ELSE 0 END) AS Incoming
FROM table1
GROUP BY LEAST(From,To), GREATEST(From,To)

我还假设From和To不能相等。

只是要完成，包含冗余行的查询：

SELECT LEAST(From,To) AS A, GREATEST(From,To) AS B, 
SUM(CASE WHEN FROM < TO THEN 1 ELSE 0 END) AS Outgoing
SUM(CASE WHEN FROM > TO THEN 1 ELSE 0 END) AS Incoming
FROM table1
GROUP BY LEAST(From,To), GREATEST(From,To)
UNION
SELECT GREATEST(From,To) AS A, LEAST(From,To) AS B, 
SUM(CASE WHEN TO < FROM THEN 1 ELSE 0 END) AS Outgoing
SUM(CASE WHEN TO > FROM THEN 1 ELSE 0 END) AS Incoming
FROM table1
GROUP BY GREATEST(From,To), LEAST(From,To)

SQL Group By为组获取2列

1 个答案: