初学者计算日期之间的天数，不包括周末和假日

Question

I am a beginner in Postgres and looking for some help on a problem I am having with a query. I am trying to count the number of business days between two dates (exclude sat & sun & holidays). This is kind of what I am trying to do:

Select column1, column2, (current_date - defined_date) as elapsed_days
from mytable
where elapsed_days excludes sat, sun, and holidays

Answer 1

create table calendar c as
(cal_date date primary key,
 business_day boolean not null);


 insert into calendar
 (select 
  ('01/01/1900'::date + (g||' days')::interval)::date,
 case extract(dow from '01/01/1900'::date 
    + (g||' days')::interval) 
 when 0 then false when 6 then false else true end
 from generate_series(0,365*150) g)

Now you have a calendar table populated with weekends set to "business_day=false" and all other days set to true.

You'll have to populate your other holidays manually or write a program to do that.

Afterwards, to calculate difference between days do something like:

 select count(*) from cal 
 where cal between "start_date_var" and "end_date_var" 
 and business_day=true;

NOTE: If it were me, I'd add a few other columns to your calendar table so that it can include which holiday it is, or other things like that. May even have another table for holidays. This is a good start though.