PostgreSQL 按季节分组（北半球和南半球）

Question

我的数据点遍布全球。每个数据点都有一个时间戳。

我想按季节对数据进行分组，如图所示（来源：https://en.wikipedia.org/wiki/Season#/media/File:Seasons1.svg）。

这是我目前尝试的方法（北半球 2011/2012 冬季）：

SELECT * FROM my_table 
    WHERE my_date BETWEEN '2011-12-21' AND '2012-03-21'
    AND ST_Y(ST_Centroid(geom)) > 0;

我怎样才能在所有可能的年份都这样做？我试过 ...OR date BETWEEN... 但这很慢。

怎么可能select南北半球都过冬？

更新

对于北半球的所有冬季数据，我使用此查询：

CREATE TABLE season_winter_north AS WITH first_step AS (
SELECT
    id,
    extract(month from my_date)::int AS month,
    extract(day from my_date)::int AS day,
    ST_Centroid(geom) AS geom
FROM mytable 
    WHERE ST_Y(ST_Centroid(geom)) > 0)

(SELECT * FROM first_step
    WHERE month = 12
        AND day >= 21)

UNION ALL

(SELECT * FROM first_step
    WHERE month = ANY('{1,2}'))

UNION ALL

(SELECT * FROM first_step
    WHERE month = 3
        AND day<21)

是否有更优雅或更高效的解决方案？

Answer 1

with t(my_date) as (
    values ('2012-07-01'::date), ('2013-03-30'), ('2013-10-12'), ('2013-01-10')
)
select 
    case 
        when my_date between 
            make_date(extract(year from my_date)::int, 3, 21)
            and
            make_date(extract(year from my_date)::int, 6, 20)
        then 'spring'
        when my_date between 
            make_date(extract(year from my_date)::int, 6, 21)
            and
            make_date(extract(year from my_date)::int, 9, 22)
        then 'summer'
        when my_date between 
            make_date(extract(year from my_date)::int, 9, 23)
            and
            make_date(extract(year from my_date)::int, 12, 20)
        then 'fall'
        else 'winter'
    end as season,
    my_date
from t
;
season |  my_date   
--------+------------
summer | 2012-07-01
spring | 2013-03-30
fall   | 2013-10-12
winter | 2013-01-10

Answer 2

我想 post 这个问题的额外答案。对于此查询，无需使用函数 make_date（仅适用于 postgresql 9.4。）。

使用此 answer 中的代码，您可以为其他版本的 PostgreSQL 创建 make_date() 函数。

我也创建了这个函数，我发现速度上存在显着差异。但是我不知道，如果make_date()函数在9.4.更快。

select 
case 
    when my_date between 
        (extract(year from my_date)::int||'-03-21')::date
        and
        (extract(year from my_date)::int||'-06-20')::date
    then 'spring'
    when my_date) between 
        (extract(year from my_date)::int||'-06-21')::date
        and
        (extract(year from my_date)::int||'-09-22')::date
    then 'summer'
    when my_date) between 
        (extract(year from my_date)::int||'-09-23')::date
        and
        (extract(year from my_date)::int||'-12-20')::date
    then 'fall'
    else 'winter'
end as season,
my_date
from my_table;

不带 make_date() 的查询比带 make_date.

的查询快 3 到 4 倍

Answer 3

更简洁，可能性能更好：

with t(my_date) as (
values ('2012-07-01'::date), ('2013-03-30'), ('2013-10-12'), ('2013-01-10') )
    select 
    case 
        when to_char(my_date,'MMDD') between '0321' and '0620' then 'spring'
        when to_char(my_date,'MMDD') between '0621' and '0922' then 'summer'
        when to_char(my_date,'MMDD') between '0923' and '1220' then 'fall'
        else                                                        'winter'
    end as season,
    my_date
    from t;

PostgreSQL 按季节分组（北半球和南半球）

PostgreSQL group by season (northern and southern hemisphere)

postgresql

date

postgis

between