计算列的 Postgresql 日期差异（以小时为单位）

Question

您好，我在 Postgresl 中创建了一个视图，除了一列之外，它可以工作。我需要它从之前的reported_date 中减去reported_date，并根据well_id 以小时为单位给出答案。我非常迷茫，我什至不介意花几块钱来解决问题。

COALESCE(g.Delta_Hours, hours_diff*24 + DATE_PART('hour',p.reported_date,'hh,start'-'hh,end'))  AS Delta_Hours
group by p.well_id,
         p.reported_date,

Answer 1

使用lag() window function 查找该井的先前报告日期。然后，只需常规减法即可从 2 个日期中得到 INTERVAL，extract(epoch from <interval>) 得到以秒为单位的增量，最后将 /3600 转换为小时。

testdb=# create table t(well_id integer, reported_date timestamp);
insert into t select 1, '2021-08-01 13:00';
insert into t select 2, '2021-08-01 13:00';
insert into t select 1, '2021-08-01 15:00';
insert into t select 2, '2021-08-01 16:00';
CREATE TABLE
INSERT 0 1
INSERT 0 1
INSERT 0 1
INSERT 0 1
testdb=# SELECT well_id, reported_date,
  extract(epoch from (reported_date -
              (lag(reported_date) over (partition by well_id order by reported_date))
  ))/3600 AS hours_since_last_date_for_this_well
from t;
 well_id |    reported_date    | hours_since_last_date_for_this_well 
---------+---------------------+-------------------------------------
       1 | 2021-08-01 13:00:00 |                                    
       1 | 2021-08-01 15:00:00 |                                   2
       2 | 2021-08-01 13:00:00 |                                    
       2 | 2021-08-01 16:00:00 |                                   3
(4 rows)

鉴于您在 cmets 中的视图定义，新的视图定义为：

CREATE OR REPLACE VIEW public.vw_production_with_gauge_time 
AS
SELECT p.well_name, p.well_type, p.well_alias, p.is_active, p.latest_production_time, p.id, p.well_id, p.produced_at, p.oil, p.gas, p.water, p.reported_date, COALESCE(g.gauge_time_local, '6:00am'::character varying) AS gauge_time_local, COALESCE(g.gauge_at_local, p.reported_date::date + '06:00:00'::interval) AS gauge_at_local, COALESCE(g.gauge_at, timezone('UTC'::text, timezone('US/Central'::text, p.reported_date::date + '06:00:00'::interval))) AS gauge_at, p.is_operating, p.hours_on, p.normal_hours_on,
extract(epoch from (p.reported_date -
              (lag(p.reported_date) over (partition by p.well_id order by p.reported_date))
  ))/3600 AS hours_since_last_date_for_this_well
FROM vw_production p LEFT JOIN vw_gauge_times g ON p.reported_date::date = g.gauge_at_local::date AND p.well_id = g.well_id ORDER BY p.reported_date DESC;