Get month days between 2 dates - sql

Question

What is the easiest way to find difference in days between 2 dates separately for each month.
Let's suppose I have two dates
1.25 May 2016
2.08 Jun 2016
The result I want to obtain is number of days for May and numbers of Day for Jun like this (201605-6,201606-8).
Which is the best method to do this?

Answer 1

In your case, start_date and end_date are in the same row of a table so one solution is:
Idea: create a function with 2 input: start_date and end_date, output: string_with_days_in_each_month_between_two_date
Practice: First, create a function GET_DAYS_EACH_MONTH_BETWEEN return the expected string with each start_date and end_date
CREATE OR REPLACE FUNCTION GET_DAYS_EACH_MONTH_BETWEEN
(start_date IN date, end_date IN date)
RETURN varchar2 IS
result varchar2(4000);
BEGIN
WITH tmp AS
(SELECT
LAST_DAY(ADD_MONTHS( start_date, level-1 ))
FROM
(SELECT
start_date
,end_date
FROM
dual)
CONNECT BY
level <= MONTHS_BETWEEN(
TRUNC(end_date,'MM'),
TRUNC(start_date,'MM') )
)
, tmp1 AS
(
SELECT start_date date_col FROM dual
UNION ALL
SELECT end_date from dual
UNION ALL
SELECT * FROM tmp
)
SELECT
LISTAGG(result_col, ',') WITHIN GROUP (ORDER BY date_col) into result
FROM
(SELECT
TO_CHAR(date_col,'yyyyMM') || '_' || TO_CHAR(date_col - LAG(date_col) OVER (ORDER BY date_col)) result_col
, date_col
,ROW_NUMBER() OVER (ORDER BY date_col) rwn
FROM
tmp1
ORDER BY
date_col
)
WHERE
rwn <> 1;
RETURN result;
END;
Second, apply your function to your table
WITH test_table AS
(
SELECT
TO_DATE('2016-02-06','yyyy-mm-dd') start_date
,TO_DATE('2016-06-08','yyyy-mm-dd') end_date
FROM
DUAL
UNION ALL
SELECT
TO_DATE('2016-05-06','yyyy-mm-dd')
,TO_DATE('2016-06-08','yyyy-mm-dd')
FROM
DUAL
)
SELECT
start_date, end_date
,GET_DAYS_EACH_MONTH_BETWEEN(start_date, end_date) result_col
FROM
test_table;
Result:
start_date end_date result_col
2/6/2016 6/8/2016 201602_23,201603_31,201604_30,201605_31,201606_8
5/6/2016 6/8/2016 201605_25,201606_8
IMPORTANCE NOTICE: the result string only have 4000 char in length, so you should consider when start_date and end_date is too far from each
The function using suggested result from this link to gerenate all months between 2 given date.

Answer 2

I made a recursive approach:
with recur (dias, texto, nivel, d1,d2) as
(select last_day(d1)-d1 as dias, to_char(d1,'yyyymm')||'-' as texto, 0 as nivel, d1,d2 from dates union all --first date
select case when (d2-trunc(add_months(d1, nivel+1),'month')+1) > extract(day from last_day(add_months(d1, nivel+1)))
then extract(day from last_day(add_months(d1, nivel+1)))
else d2-trunc(add_months(d1, nivel+1),'month')+1 end as dias,
to_char(add_months(d1, nivel+1),'yyyymm')||'-' as texto, nivel+1 as nivel ,d1,d2 from recur where trunc(add_months(d1, nivel+1),'month') < d2 --last month
)
select d1, d2,listagg(texto||to_char(dias),',') within group (order by nivel) as resultado
from recur
group by d1,d2
order by d1,d2;
OUTPUT for 25 May 2016 to 08 Jun 2016
25-MAY-16 08-JUN-16 201605-6,201606-8
OUTPUT for 25 May 2016 to 08 Jul 2017
25-MAY-16 08-JUL-17 201605-6,201606-30,201607-31,201608-31,201609-30,201610-31,201611-30,201612-31,201701-31,201702-28,201703-31,201704-30,201705-31,201706-30,201707-8