Question

我正在编写一个查询，该查询将许多位置与公交车站列表连接起来，以便确定距公共公交车站的最小距离。使用查询非常简单：

select
  location.id,
  MIN(
    ST_distance_sphere(
      ST_MakePoint(
        transit.latitude,
        transit.longitude
      ),
      ST_MakePoint(
        cast(locations.latitude as double precision),
        cast(locations.longitude as double precision)
      )
    )
  ) as meters_from_nearest_stop,
from public.transit_stops transit
cross join public.locations locations
group by 1

但是，这不能天真地给我最小距离的位置，而只是最小距离。如何修改此设置，以便以最小的距离返回行中的其他属性？

产生的交叉联接相当大，因此性能很重要。

Answer 1

这是通过row_number（）函数完成的，如下所示：

select *, 
    row_number() over (partition by location.id order by meters_from_nearest_stop) as closest
from (
    select
      location.id,
      transit.id,
      ST_distance_sphere(
          ST_MakePoint(
            transit.latitude,
            transit.longitude
          ),
          ST_MakePoint(
            cast(locations.latitude as double precision),
            cast(locations.longitude as double precision)
          )
        )
      as meters_from_nearest_stop,
    from public.transit_stops transit
    cross join public.locations locations
) q
where closest=1

从交叉联接的最少行中选择其他属性

1 个答案: