在 postgresql 中加入两个选择查询答案

【问题标题】：joining two select queries in postgresql在 postgresql 中加入两个选择查询
【发布时间】：2017-04-30 14:56:45
【问题描述】：

这是我的第一个选择查询

SELECT date_trunc('hour',start_time) as time , extract(day from start_time) as day ,start_zone_id as zone_id, count(*) as booking_trips
  FROM public.trip_information_september where trip_type='{BOOKING}' group by date_trunc('hour',start_time ), start_zone_id ,extract(day from start_time) ORDER BY time,start_zone_id

这是我的第二个选择查询

  SELECT date_trunc('hour',start_time) as time , extract(day from start_time) as day ,start_zone_id as zone_id, count(*) as booking_trips
      FROM public.trip_information_september where trip_type='{NO_INFO}' group by date_trunc('hour',start_time ), start_zone_id ,extract(day from start_time) ORDER BY time,start_zone_id

所以当我加入这两个时

select * from
  (SELECT date_trunc('hour',start_time) as time , extract(day from start_time) as day ,start_zone_id as zone_id, count(*) as booking_trips
  FROM public.trip_information_september where trip_type='{BOOKING}' group by date_trunc('hour',start_time ), start_zone_id ,extract(day from start_time) ORDER BY time,start_zone_id )A
  INNER JOIN
  (SELECT date_trunc('hour',start_time ) as time,extract(day from start_time) as day, start_zone_id as zone_id, count(*) as normal_trips
  FROM public.trip_information_september where trip_type='{NORMAL}' group by date_trunc('hour',start_time ), start_zone_id ,extract(day from start_time) ORDER BY time,start_zone_id) B

  ON A.time=B.time and A.zone_id=B.zone_id and A.day=B.day limit 100 ;

我得到时间、日期、zone_id 两次，而不是加入的一次。任何帮助表示赞赏。

【问题讨论】：

标签： database postgresql join

【解决方案1】：

这并不奇怪，因为您的子查询连接被包装在一个外部查询中，它执行 SELECT * 您想要类似的东西

SELECT A.time, A.day, A.zone_id, booking_trips /*, ... REST OF THE REQUIRED COLUMNS */ FROM

(SELECT date_trunc('hour',start_time) as time , extract(day from start_time) as day ,start_zone_id as zone_id, count(*) as booking_trips
  FROM public.trip_information_september where trip_type='{BOOKING}' group by date_trunc('hour',start_time ), start_zone_id ,extract(day from start_time) ORDER BY time,start_zone_id )A
  INNER JOIN
  (SELECT date_trunc('hour',start_time ) as time,extract(day from start_time) as day, start_zone_id as zone_id, count(*) as normal_trips
  FROM public.trip_information_september where trip_type='{NORMAL}' group by date_trunc('hour',start_time ), start_zone_id ,extract(day from start_time) ORDER BY time,start_zone_id) B

  ON A.time=B.time and A.zone_id=B.zone_id and A.day=B.day limit 100 ;

【讨论】：