嗨,我正在尝试通过Postgresql数据库中的纬度和经度查找最近的位置。但是当我运行以下查询时,它显示的列距离不存在。
ERROR: column "distance" does not exist
LINE 1: ... ) ) ) AS distance FROM station_location HAVING distance <...
^
********** Error **********
ERROR: column "distance" does not exist
SQL state: 42703
Character: 218
CREATE TABLE station_location
(
id bigint NOT NULL DEFAULT nextval('location_id_seq'::regclass),
state_name character varying NOT NULL,
country_name character varying NOT NULL,
locality character varying NOT NULL,
created_date timestamp without time zone NOT NULL,
is_delete boolean NOT NULL DEFAULT false,
lat double precision,
lng double precision,
CONSTRAINT location_pkey PRIMARY KEY (id)
)
SELECT *,( 3959 * acos( cos( radians(6.414478) ) * cos( radians( lat ) ) * cos( radians( lng ) - radians(12.466646) ) + sin( radians(6.414478) ) * sin( radians( lat ) ) ) ) AS distance
FROM station_location
HAVING distance < 5
ORDER BY distance
LIMIT 20;
select * from (
SELECT *,( 3959 * acos( cos( radians(6.414478) ) * cos( radians( lat ) ) * cos( radians( lng ) - radians(12.466646) ) + sin( radians(6.414478) ) * sin( radians( lat ) ) ) ) AS distance
FROM station_location
) al
where distance < 5
ORDER BY distance
LIMIT 20;
不要在这样的桌子上长期存放经纬度。而是使用PostGIS几何图形或geography type。
CREATE EXTENSION postgis;
CREATE TABLE foo (
geog geography;
);
CREATE INDEX ON foo USING gist(geog);
INSERT INTO foo (geog)
VALUES (ST_MakePoint(x,y));
现在,当您需要查询它时,您可以使用KNN (<->
)实际在索引上执行此操作。
<->
在查询中,您明确拥有SELECT *
FROM foo
ORDER BY foo.geog <-> ST_MakePoint(x,y)::geography;
。您也可以在索引上执行此操作。
HAVING distance < 5
如果所有点都位于SELECT *
FROM foo
WHERE ST_DWithin(foo.geog, ST_MakePoint(x,y)::geography, distance_in_meters)
ORDER BY foo.geog <-> ST_MakePoint(x,y)::geography;
之外,这将确保不返回任何内容。
此外,x和y是十进制数字distance_in_meters
请参见ST_MakePoint(46.06, 14.505)
,您将找到如何在this gist类型上声明DOMAIN,以及如何重写point
运算符以返回矫正距离。
声明从distance
继承的latlong
类型:
point
以公里为单位的矫正距离(在具有地球半径的球面上的距离:]
CREATE DOMAIN latlong AS point CHECK (VALUE[0] BETWEEN -90.0 AND 90.0 AND VALUE[1] BETWEEN -180 AND 180);
与拉特隆一起使用时,请使用此功能覆盖距离运算符CREATE OR REPLACE FUNCTION orthodromic_distance(latlong, latlong) RETURNS float AS $_$
SELECT acos(
sin(radians($1[0]))
*
sin(radians($2[0]))
+
cos(radians($1[0]))
*
cos(radians($2[0]))
*
cos(radians($2[1])
-
radians($1[1]))
) * 6370.0;
$_$ LANGUAGE sql IMMUTABLE;
:
<->
现在在您的SQL查询中,找到最近的实体:
CREATE OPERATOR <-> ( PROCEDURE = orthodromic_distance
, LEFTARG = latlong, RIGHTARG = latlong
);
您可能想使用latlong类型将位置WITH
station_distance AS (
SELECT
id AS station_id,
point(lat, long)::latlong <-> point(6.414478, 12.466646)::latlong AS distance
FROM station_location
WHERE NOT is_deleted
)
SELECT
sl.state_name,
sl.country_name,
sl.locality,
point(sl.lat, sl.long)::latlong AS coordinates,
sd.distance
FROM
station_location sl
JOIN station_distance sd
ON sd.station_id = sl.id
ORDER BY
distance ASC
LIMIT 10
和lat
存储在同一字段中。
手册阐明:
输出列的名称可以用来引用列中的值ORDER BY和GROUP BY子句,但不在WHERE或HAVING子句中;在那里,您必须改写表达式。