Extracting year and total days between range of date - SQL - mysql

Question

I have data with start date and end date (Say 20th Feb 2018 to 20th Feb 2020), I want to find out the total days in every year inside this range.
For example:
2018 - x days
, 2019 - 365 days
, 2020 - y days etc.
Is there a way I can do in SQL without hardcoding year values?
I tried hardcoding the values and it worked well. But I want a solution without hardcoding year values

Answer 1

I'm not familiar enough with MySql to know if this will port, however here is a tested and confirmed SQL Server solution.
The fiddle link is here for your use.
Given start dates 02/20/2018 and 02/20/2020, the result set is as follows:
Year
periodStart
periodEnd
DaysInPeriod
2018
2018-02-20
2018-12-31
314
2019
2019-01-01
2019-12-31
365
2020
2020-01-01
2020-02-20
51
Declare #StartDate date = '2018-02-20', #EndDate date = '2020-02-20';
WITH x AS (SELECT n FROM (VALUES (0),(1),(2),(3),(4),(5),(6),(7),(8),(9)) v(n)),
Years AS (
SELECT ROW_NUMBER() OVER (ORDER BY (SELECT NULL)) AS Year
FROM x ones, x tens, x hundreds, x thousands)
SELECT Years.Year,
CASE
WHEN Year(#StartDate) = Years.year THEN #StartDate
ELSE DATEFROMPARTS(years.year, 01, 01)
END AS periodStart,
CASE
WHEN Year(#EndDate) = Years.year THEN #EndDate
ELSE DATEFROMPARTS(years.year, 12, 31)
END AS periodEnd,
DATEDIFF(day,
CASE
WHEN Year(#StartDate) = Years.year THEN #StartDate
ELSE DATEFROMPARTS(years.year, 01, 01)
END,
CASE
WHEN Year(#EndDate) = Years.year THEN #EndDate
ELSE DATEFROMPARTS(years.year, 12, 31)
END
) + 1 AS DaysInPeriod
FROM Years
WHERE Years.Year >= Year(#StartDate)
AND Years.Year <= Year(#EndDate)

Answer 2

Using WITH RECURSIVE to create range of dates then we can easly count the number of days for each year using DATEDIFF
WITH RECURSIVE dates AS
(
SELECT min(start_date) as start_date, DATE_FORMAT(min(start_date),'%Y-12-31') as last_day FROM mytable
UNION ALL
SELECT DATE_FORMAT(start_date + INTERVAL 1 YEAR,'%Y-01-01'),
DATE_FORMAT(start_date + INTERVAL 1 YEAR,'%Y-12-31')
FROM dates
WHERE DATE_FORMAT(start_date + INTERVAL 1 YEAR,'%Y-01-01') <= (SELECT MAX(end_date) FROM mytable)
),
cte2 as (
SELECT d.start_date as start_day, if(YEAR(d.start_date) = YEAR(m.end_date), m.end_date, d.last_day) as last_day
FROM dates d, mytable m
)
select *, DATEDIFF(last_day, start_day)+1 as total_days
from cte2;
Demo here

Answer 3

You are looking for the DATEDIFF function.
https://dev.mysql.com/doc/refman/8.0/en/date-and-time-functions.html#function_datediff
DATEDIFF() returns expr1 − expr2 expressed as a value in days from one date to the other. expr1 and expr2 are date or date-and-time expressions.
You are free to specify e.g. "2019-01-01" or "2020-01-01"
as input arguments to DATEDIFF.
You may find it convenient to store several January 1st
dates in a calendar reporting table, if you want SELECT to loop
over several years and report on number of days in each year.