Select records by month and year between two dates - sql

Question

I have the table record_b. I want to select the records of an specific month and year between begin_date and end_date.
id
begin_date
end_date
2
2022-09-04
2022-10-03
3
2022-10-04
2022-10-31
4
2022-11-04
2022-12-03
5
2022-12-04
2023-01-03
6
2023-01-04
2023-02-03
7
2023-02-04
null
eg1:
Input: 2023-01
Output should be the record with id 5 and 6
eg2:
Input: 2022-12
Output should be the record with id 4 and 5
I have tried using between however there is a problem evaluating the months after the year.
and v_year BETWEEN EXTRACT(YEAR FROM PC.begin_date)
AND EXTRACT(YEAR FROM PC.end_date)
AND v_month BETWEEN EXTRACT(MONTH FROM PC.begin_date)
AND EXTRACT(MONTH FROM PC.end_date)

Answer 1

A very basic dictate is when you have a date store it as a date.
This can be further extended to when you need to process dates then process dates.
Most of the nothing else will be needed - no conversion, extract, date_part, epoch - just dates.
The task here is to find those rows where a specified Year-Month (yyyy-mm) falls within the period begin and end dates from a table.
Realize that if any portion of the specified year-month falls within the period then the first day of that month (yyyy-mm-01) falls within that period.
You can use the make_date() function to get the first of the specified month. Then JOIN that result with between dates.
with input_val(yr_mon) as (values (:yyyymm)) --select * from input_val
, tgt_date(dt) as
( select 0make_date(substring(yr_mon,1,4)::integer
,substring(yr_mon,6,2)::integer
,01
)
from input_val
) --select * from tgt_date;
select rb.*
from tgt_date t
join record_b rb
on t.dt between date_trunc('month',rb.begin_date)
and date_trunc('month',rb.end_date);
The above however does NOT handle well data point 7 with a null end date (nor would it handle a null start date). But should it?
If so a null value is often interpreted as there in no ending date, which basically says all dates on or after the start date are included.
You can handle the situation by converting the period to a daterange, which will handle it without getting into null processing logic, then use the range containment operator.
with input_val(yr_mon) as (values (:yyyymm)) --select * from input_val
, tgt_date(dt) as
( select make_date(substring(yr_mon,1,4)::integer
,substring(yr_mon,6,2)::integer
,01
)
from input_val
) --select * from tgt_date;
select rb.*
from tgt_date t
join record_b rb
on t.dt <# daterange(date_trunc('month',rb.begin_date)::date
,date_trunc('month',rb.end_date)::date
, '[]'
);
Finally, depending on how you you use the results, you can hide this whole thing within a SQL function, which can then be used in an SQL statement.
create or replace function periods_with_year_month(year_mm text)
returns setof record_b
language sql
as $$
with tgt_date(dt) as
(select make_date(substring(year_mm,1,4)::integer
,substring(year_mm,6,2)::integer
,01
)
)
select rb.*
from tgt_date t
join record_b rb
on t.dt <# daterange( date_trunc('month',rb.begin_date)::date
, date_trunc('month',rb.end_date)::date
, '[]'
);
$$;
See demo here. Unfortunately ,db<>fiddle is non-interactive, so parameters of yyyy-mm are hard coded.