Question

嗨我有一个问题，我有一张桌子如下：

from_city  to_city      Distance
bangalore  chennai      350
chennai    Bangalore    350
mumbai     bangalore    500
bangalore  Mumbai       500
Mumbai     Delhi        500
Delhi      Mumbai       500

我可以在这里得到如下答案：

bangalore  chennai     350
Mumbai     Bangalore   500
Mumbai     Delhi       500

答案可以是bangalore-chennai或channai-bangalore。因为两种方式都有相同的距离。我每个城市只需要一个入口。我怎么能实现它？答案应该是一般性的。 tommorrrow如果添加其他城市像bangalore -mysore或mysore-bangalore，我只需要输入。

Answer 1

一种方法是使用distinct与case：

select distinct
  case when lower(from_city) < lower(to_city) 
        then Initcap(from_city) else Initcap(to_city) end as from_city,
  case when lower(from_city) < lower(to_city) 
        then Initcap(to_city) else Initcap(from_city) end as to_city,
  Distance
from t;

产地：

FROM_CITY   TO_CITY     DISTANCE
--------------------------------
Delhi       Mumbai      500
Bangalore   Mumbai      500
Bangalore   Chennai     350

查询从表中查找单个条目

1 个答案: