根据ISO标准，2015和2016年的每个月有多少周？

Question

今年2014年有：

Jan-4
Feb-4
Mar-5
Apr-4
May-4
Jun-5
Jul-4
Aug-4
Sep-5
Oct-4
Nov-4
Dec-5

如何计算任何给定年份的这一点？

Answer 1

按照建议的here将ISO8601应用到一个月

select
    to_char(d, 'YYYY Mon') as "Month",
    case when
        extract(dow from d) in (2,3,4)
        and
        extract(day from (d + interval '1 month')::date - 1) + extract(dow from d) >= 33
        then 5
        else 4
    end as weeks
from generate_series(
    '2014-01-01'::date, '2014-12-31', '1 month'
) g (d)
;
  Month   | weeks 
----------+-------
 2014 Jan |     5
 2014 Feb |     4
 2014 Mar |     4
 2014 Apr |     4
 2014 May |     5
 2014 Jun |     4
 2014 Jul |     5
 2014 Aug |     4
 2014 Sep |     4
 2014 Oct |     5
 2014 Nov |     4
 2014 Dec |     4