ST_Distance 函数的 postgis postgres 计数和按列分组答案

【问题标题】：postgis postgres count and group by column for ST_Distance functionST_Distance 函数的 postgis postgres 计数和按列分组
【发布时间】：2015-11-03 10:51:21
【问题描述】：

此 SQL 产生以下内容：

SELECT city FROM travel_logs ORDER BY ST_Distance(travel_logs.start_point, ST_GeographyFromText('SRID=4326;POINT(101.652506 3.167610)')) 

"Tshopo"
"Tshopo"
"Mongala"
"Haut-Komo"

此 SQL 产生以下内容：

SELECT city, count(*) AS count FROM travel_logs GROUP BY travel_logs.start_point, city ORDER BY ST_Distance(travel_logs.start_point, ST_GeographyFromText('SRID=4326;POINT(101.652506 3.167610)')) 

"Tshopo";1
"Tshopo";1
"Mongala";1
"Haut-Komo";1

基本上，我想要这样的结果，按城市和同一城市出现的次数分组。像这样的

"Tshopo";2  <--- its summed up correctly
"Mongala";1
"Haut-Komo";1

我不是联接、子查询方面的专家，这有帮助吗？提前致谢。

【问题讨论】：

标签： sql postgresql count group-by postgis

【解决方案1】：

这对我有用：

select city, count(*) as count
from
(SELECT city FROM travel_logs ORDER BY ST_Distance(travel_logs.start_point, ST_GeographyFromText('SRID=4326;POINT(101.652506 3.167610)'))
) as subquery_travel_logs_nearest group by city

【讨论】：

【解决方案2】：

没有子查询的简单、普通的 SQL：

SELECT city, count(*)
FROM travel_logs
GROUP BY city
ORDER BY ST_Distance(start_point,
         ST_GeographyFromText('SRID=4326;POINT(101.652506 3.167610)'));

【讨论】：