[英]Creating N days interval function in postgresql
I am trying to create a function in postgresql that returns a set of dates in between two dates with a certain interval.我正在尝试在 postgresql 中创建一个 function ,它返回两个日期之间具有一定间隔的一组日期。 For example, If I pass on these two date parameters like
most_recent_day = 2020-01-10
and mininum_day = 2020-01-01
and this interval parameter n_day_group_interval = 5
, the function will return the following set:例如,如果我传递这两个日期参数,例如
most_recent_day = 2020-01-10
和mininum_day = 2020-01-01
以及此间隔参数n_day_group_interval = 5
,则 function 将返回以下集合:
2020-01-10
2020-01-08
2020-01-06
2020-01-04
2020-01-02
Following was my attempt that gives an syntax error at or near "end"
.以下是我
syntax error at or near "end"
尝试。 Thank you for your help.谢谢您的帮助。
create function get_n_day_group_dates(most_recent_day date, minimum_day date, n_day_group_interval varchar)
returns table (
n_day_group_dates date
)
as $body$
begin
return query
SELECT
date_trunc('day'::text, dd.dd)::date AS n_day_group_dates
FROM
LATERAL generate_series(most_recent_day,
minimum_day,
'-'||n_day_group_interval||' day'::interval) dd(dd)
end;
$body$
language plpgsql;
You are overcomplicating things.你把事情复杂化了。 LATERAL is not required and
date_trunc('day', ..)
is the same as casting to date
. LATERAL 不是必需的,
date_trunc('day', ..)
与强制转换为date
相同。
To create an interval based on a variable, the easiest way is to use make_interval()
要基于变量创建间隔,最简单的方法是使用
make_interval()
create function get_n_day_group_dates(most_recent_day date, minimum_day date, n_day_group_interval varchar)
returns table (n_day_group_dates date)
as $body$
SELECT g.dt::date
FROM generate_series(most_recent_day,
minimum_day,
make_interval(days => n_day_group_interval) as g(dt);
$body$
language sql;
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