Question

我试图检索距离一组XY坐标最远的所有目击事件，我能够检索先前查询中给出最大距离的第一行。但是，如果在同一坐标处发生目击，它无法处理多个最大值。

我尝试了两种不同的方法来尝试获得最大值：

WITH params as (
          SELECT -28 as lat, 151 as lon
          FROM dual
         )
    SELECT sighting_id, sqrt(power(lat - latitude, 2) + power(lon - longitude,  2)
    ) 
    AS distance

    FROM sightings CROSS JOIN params

    WHERE sqrt(power(lat - latitude, 2) + power(lon - longitude, 2)) = 
     (select * from (select sighting_id, 
      sqrt(power(lat - latitude, 2) + power(lon - longitude, 2)) 

    FROM sightings CROSS JOIN params

    ORDER BY sqrt(power(lat - latitude, 2) + power(lon - longitude, 2)) desc )

    WHERE rownum <= 1);

和

WITH params as (
              SELECT -28 as lat, 151 as lon
              FROM dual
             )
        SELECT sighting_id, sqrt(power(lat - latitude, 2) + power(lon - longitude,  2)
        ) 
        AS distance

        FROM sightings CROSS JOIN params

        WHERE sqrt(power(lat - latitude, 2) + power(lon - longitude, 2)) = 
         (SELECT MAX(sqrt(power(lat - latitude, 2) + power(lon - longitude, 2))) 

        FROM sightings CROSS JOIN params);

第一种方式错误说太多的值，第二种方式说我不能使用MAX（）超过欧几里德距离。我该如何克服这个问题？

Answer 1

据我了解你想要占用最大距离。你可以尝试下面的一个，让我知道它是否有效？

WITH params AS （SELECT -28 AS lat，151 AS lon 从双方）选择sighting_id，距离 FROM（SELECT sighting_id， SQRT（POWER（纬度 - 纬度，2）+ POWER（经度 - 经度，2））AS距离， MAX（SQRT（POWER（纬度 - 纬度，2） + POWER（经度 - 经度，2）））OVER（PARINGTION by sighting_id）AS max_distance 从目击CROSS JOIN params ）dat WHERE dat.distance = max_distance

此致，Niraj

Answer 2

在第一个查询中，你在where子句中犯了两个错误。您尝试比较read() returns -1。 ServerSocket返回多个值。接下来，你从零开始尝试SQRT(...) = select * ...。你应该指出它。你可以把它重写为

Select *...

或

select sighting_id, 
      sqrt(power(lat - latitude, 2) + power(lon - longitude, 2)

或用分析函数重写它

WITH params as (
      SELECT -28 as lat, 151 as lon
      FROM dual
     )
SELECT sighting_id, 
       sqrt(power(lat - latitude, 2) + power(lon - longitude,  2))  AS distance
FROM sightings 
CROSS JOIN params
WHERE sqrt(power(lat - latitude, 2) + power(lon - longitude, 2)) = 
 (select max_value 
   from ( select sqrt(power(lat - latitude, 2) + power(lon - longitude, 2) as max_value  
         FROM sightings CROSS JOIN param
         order by sqrt(power(lat - latitude, 2) + power(lon - longitude, 2) desc)
  where rownum <=1)  
ORDER BY sqrt(power(lat - latitude, 2) + power(lon - longitude, 2)) desc ));

获得最大值

2 个答案: