Question

我正在尝试对我的表执行查询：所以这是详细的方法：

通过先恢复搜索来限制搜索：选择200公里以内的点的所有ID， -然后选择两个点之间的距离为300并且Received_c相同的id -返回这些ID，按_id

分组

SELECT rxg._id 
FROM (
      SELECT *  FROM ais 
      WHERE ST_DWithin(geography(point), 
      ST_SetSRID(ST_MakePoint(-95.0217,29.6111), 4326)::geography, 
      200000)
) 
AS rxg, rxg AS b
WHERE ST_DWITHIN (rxg.point, b.point, 300) 
AND rxg._id != b._id
AND rxg.received_c = b.received_c
GROUP BY _id
;

Answer 1

我认为您遇到的问题是，您尝试两次使用一个子查询，但是您不能这样做。相反，请尝试在此处使用公用表表达式（CTE），该表将对该子查询的代码内联两次：

WITH cte AS (
    SELECT *
    FROM ais 
    WHERE ST_DWithin(geography(point), 
        ST_SetSRID(ST_MakePoint(-95.0217,29.6111), 4326)::geography, 
        200000)
)

SELECT rxg._id
FROM cte rxg
INNER JOIN cte b
    ON rxg._id != b._id AND
       rxg.received_c = b.received_c
WHERE ST_DWITHIN (rxg.point, b.point, 300)
GROUP BY rxg._id;

还要注意，我用隐式内部联接替换了您的旧式隐式联接。自ANSI-92标准以来，这是连接表的首选方式。

如何构造多重选择查询错误：关系“ rxg”不存在

1 个答案: