CartoDB 中的 PostgreSQL "column does not exist" 错误

Question

我目前正在处理一个查询，该查询应该 return CartoDB table 的子集（即新的 table）按与给定点的接近程度排序。我想在地图上显示与最近、第二最近等相对应的标签，并想通过在新列中使用 PostgreSQL row_number() 方法来捕获它：

SELECT
    *,
    ST_Distance(
        ST_GeomFromText('Point(-73.95623080000001 40.6738101)', 4326)::geography,
        the_geom::geography
    ) / 1609 AS dist,
    row_number() OVER (ORDER BY dist) as rownum
FROM locations
WHERE ST_Intersects(
   ST_GeomFromText(
      'Point(-73.95623080000001 40.6738101)', 4326
   ),
   the_geom
)
ORDER BY dist ASC

但是，当我尝试这样做时，CartoDB/PostgreSQL return出现以下错误：

Error: column "dist" does not exist

关于更好的方法或我遗漏的东西有什么建议吗？

Answer 1

您不能在另一列中使用列别名。在这里，您为结果列表定义了 dist，并且还在 row_number 的 ORDER BY 中使用了它。您必须改写用于 order 的相同表达式。

Answer 2

您不能使用在同一级别计算的字段。

SELECT (x1-x2)^2 + (y1-x2)^2  as dist, dist * 1.6 as miles
                                       ^^^^^
                                    undefined

所以你创建了一个子查询。

SELECT dist * 1.6 as miles
FROM ( SELECT (x1-x2)^2 + (y1-x2)^2  as dist
       FROM table
     ) T

Answer 3

SELECT *,
    row_number() OVER (ORDER BY dist) as rownum
FROM(
SELECT
    *,
    ST_Distance(
        ST_GeomFromText('Point(-73.95623080000001 40.6738101)', 4326)::geography,
        the_geom::geography
    ) / 1609 AS dist
FROM locations
WHERE ST_Intersects(
   ST_GeomFromText(
      'Point(-73.95623080000001 40.6738101)', 4326
   ),
   the_geom
)
) i
ORDER BY dist ASC

您无法从同一个 select 访问别名，因此请将其放在内部查询中

Answer 4

虽然可以使用派生的内部查询（它可能更容易阅读并且可以根据其他 RA 规则进行优化），但也可以使用 ordinals 来请参考列，因为限制仅适用于新引入的 names.

例如，以下是有效的：

SELECT
    ST_Distance(
        ST_GeomFromText('Point(-73.95623080000001 40.6738101)', 4326)::geography,
        the_geom::geography
    ) / 1609 AS dist
  -- column ordering changed to make ordinal obvious, as * can bite
  -- now column 'dist' is the first column and can be referenced by ordinal
  , row_number() OVER (ORDER BY 1) as rownum
  , *
FROM locations
WHERE ST_Intersects(
   ST_GeomFromText(
      'Point(-73.95623080000001 40.6738101)', 4326
   ),
   the_geom
)
-- this could also be written as ORDER BY 1 ASC, per ordinal
ORDER BY dist ASC

CartoDB 中的 PostgreSQL "column does not exist" 错误

PostgreSQL "column does not exist" error in CartoDB

sql

postgresql

postgis

cartodb