如何在社交网络分析（SNA）中使用SQL来获取两列之间的平均值来压缩行

Question

我有三列：发件人，收件人，短信息＃。

我需要通过获取两列的平均值来压缩行。

因此，假设Carol发送了Jack 8短信，而Jack发送了Carol 4短信，结果将是这两个人之间的6条消息。

有关更好的说明，请参见下图。

enter image description here

Answer 1

在SQL中执行此操作的典型方法如下：

select least(sender, receiver) as person1,
       greatest(sender, receiver) as person2,
       sum(num)
from t
group by least(sender, receiver),
         greatest(sender, receiver);

有些数据库不支持least()和greatest()。这些可以用case表达式代替。

select (case when sender < receiver then sender else receiver end) as person1,
       (case when sender >= receiver then sender else receiver end) as person2,
       sum(num)
from t
group by (case when sender < receiver then sender else receiver end), 
          (case when sender >= receiver then sender else receiver end);