Dynamic due date finder in a single query - mysql

Question

id start_date interval period
1 2018-01-22 2 month
2 2018-02-25 3 week
3 2017-11-24 3 day
4 2017-07-22 1 year
5 2018-02-25 2 week
the above is my table data sample. start_dates will be expired based on interval and period(i.e id-1 will have due date after 2 months from the start_date, id-2 will have due after 3 weeks vice versa). period is enum of (day,week,month,year). requirement is, Client can give any period of dates. let's say 25-06-2026 to 13-07-2026 like that.. I have to return the ids whose due dates falls under that period.I hope i made my question clear.
I am using mysql 5.7. I found a way to achieve this with recursive CTE's.(not available in mysql 5.7). and there is a way to achieve this by populating virtual records by using inline sub queries along with unions but its a performance killer and we can't do populate virtual records every time a client request comes.(like given in the link Generating a series of dates) I have reached a point to get results for a single date which is very easy. Below is my query.
SELECT b.*
FROM (SELECT a.*,
CASE
WHEN period = 'week' THEN MOD(Datediff('2018-07-22', start_date), 7 * intervals)
WHEN period = 'month'
AND Day('2018-07-22') = Day(start_date)
AND MOD(Period_diff(201807, Extract(YEAR_MONTH FROM start_date)), intervals) = 0 THEN 0
WHEN period = 'year'
AND Day('2018-07-22') = Day(start_date)
AND MOD(Period_diff(201807, Extract(
YEAR_MONTH FROM start_date)) / 12,
intervals) = 0 THEN 0
WHEN period = 'day' THEN MOD(Datediff('2018-07-22', start_date) , intervals)
end filters
FROM kml_subs a)b
WHERE b.filters = 0;
But I need to do this for a period of dates not a single date. Any suggestions or solutions will be much appreciated.
My desired result shoud be like..
if i give two dates.say 2030-05-21 & 2030-05-27. due dates falls under those 6 dates between(2030-05-21 & 2030-05-27) will be shown in the result.
id
1
4
My question is different from Using DATE_ADD with a Column Name as the Interval Value . I am expecting a dynamic way to check due dates based on start_date
Thanks, Kannan

Answer 1

In MySQL, it would seem that a query along these lines would suffice. (Almost) everything else could and should be handled in application level code...
SELECT *
, CASE my_period WHEN 'day' THEN start_date + INTERVAL my_interval DAY
WHEN 'week' THEN start_date + INTERVAL my_interval WEEK
WHEN 'month' THEN start_date + INTERVAL my_interval MONTH
WHEN 'year' THEN start_date + INTERVAL my_interval YEAR
END due_date
FROM my_table;