sql - 或者在 postgres 中按字段分组

Question

我在 psql 中有这两个查询:

select a.name, a.port, count(a.id) as cont 
from a 
group by a.name, a.port 
order by cont desc 
limit 5;

select a.name, a.ip, count(a.id) as cont 
from a 
group by a.name, a.ip 
order by cont desc 
limit 5;

我想编写一个查询，通过这 2 个组的计数获取前 5 条记录，并显示它们的 a.name、count、a.port/a.ip 字段。有谁知道如何构造此查询？

我想要这样的东西:

select a.name, a.port or a.ip, count(a.id) as cont 
from a 
group by a.name, a.port or a.ip 
order by cont desc 
limit 5;

感谢任何有关如何在 postgres 中执行此操作的指导。

Answer 1

假设 port/ip 有兼容的类型，那么横向连接是最好的解决方案:

select a.name, v.which, v.val, count(*) as cont
from a cross join lateral
     (values ('ip', ip), ('port', port)
     ) v(which, val)
group by a.name, v.which, v.val
order by cont desc
limit 5;

如果它们的类型不同，可以使用::text将它们转换为字符串:

     (values ('ip', ip::text), ('port', port::text)
     ) v(which, val)