Generic end date of quarter, PostgreSQL
-
08-10-2020 - |
Question
I'd like to produce the generic quarter end date for a given date.
Ex:If I have 2010-01-01
, I would like to return 2010-03-31
, and so on.
I can get the quarter number and year:
select to_char(date_trunc('quarter', current_date)::date, 'yyyy-q');
Which returns 2017-3
since today is 2017-07-14
How do I get the quarter end date nicely?
I can get the answer, but its very ugly:
select to_char(date_trunc('year', date '2015-01-01'),'yyyy') || '-' ||case
when (select extract('quarter' from date_trunc('quarter', date '2015-01-01')::date )) = 1 then '03-31'
when (select extract('quarter' from date_trunc('quarter', date '2015-01-01')::date )) = 2 then '06-30'
when (select extract('quarter' from date_trunc('quarter', date '2015-01-01')::date )) = 3 then '09-30'
when (select extract('quarter' from date_trunc('quarter', date '2015-01-01')::date )) = 4 then '12-31'
else '?'
end
Which returns 2015-03-31
since I put in 2015-01-01
.
Is there a better way?
Solution
I think the shortest and most elegant way to solve this issue is to use date_trunc('quarter',d)
(which will retrieve the start of the quarter) + 3 months - 1 day, and use the expression to create a FUNCTION
:
CREATE FUNCTION end_of_quarter (d date)
RETURNS date AS
$$
SELECT
CAST(date_trunc('quarter', d) + interval '3 months' - interval '1 day' AS date)
$$
LANGUAGE SQL IMMUTABLE ;
... and then use it:
SELECT
d, end_of_quarter(d)
FROM
(SELECT
CAST(d0 AS date) AS d
FROM
generate_series(date '2017-01-01', date '2017-12-31', interval '6 days') AS s(d0)
) AS q ;
d | end_of_quarter :---------- | :------------- 2017-01-01 | 2017-03-31 ... 2017-03-26 | 2017-03-31 2017-04-01 | 2017-06-30 ... 2017-06-18 | 2017-06-30 2017-07-06 | 2017-09-30 2017-07-12 | 2017-09-30 ... 2017-09-22 | 2017-09-30 2017-09-28 | 2017-09-30 2017-10-04 | 2017-12-31 2017-10-10 | 2017-12-31 ... 2017-12-21 | 2017-12-31 2017-12-27 | 2017-12-31
You can check it at dbfiddle here
You could also shorten a bit your original approach by using the simple version of CASE expression WHEN value THEN ...
:
SELECT
d,
extract('year' from d) || '-' ||
/* case expression when value instead of case when expression */
case extract('quarter' from d)
when 1 then '03-31'
when 2 then '06-30'
when 3 then '09-30'
else '12-31'
end AS end_of_quarter
FROM
generate_series(date '2017-01-01', date '2017-12-31', interval '6 days') AS s(d) ;
You can check it at dbfiddle here
If you need to do this very often, define a function:
CREATE FUNCTION end_of_quarter (d date)
RETURNS date AS
$$
SELECT
cast (extract('year' from d) || '-' ||
case extract('quarter' from d)
when 1 then '03-31'
when 2 then '06-30'
when 3 then '09-30'
else '12-31'
end
AS date)
$$
LANGUAGE SQL IMMUTABLE ;
dbfiddle here