确定日期范围内的天数

Question

I am very much new to the mysql and sincere apologies as struggling to find the right approach for the question.

I have a table which is containing the events schedule time:

Event_id 1 will be running on every Monday in between 03-04-2022 to 03-12-2022.I need to find the total run count of the each Event_id in between a date range.

Answer 1

You need to find number of day between start and end date. Eg how many Monday between start and end date for event_id=1 and so on.

In the question start_date and end_date for event_id=4 are not correct as start_date > end_date. Also, there is a spelling mistake in day name for evnet_id=4.

The query used for getting the result, after fixing data issues is -

WITH RECURSIVE 
date_gen (gen_dt) AS
(
SELECT min(start_date) from event_tab
union all
SELECT date_add(gen_dt,interval 1 day) from date_gen where gen_dt < (select max(end_date) from event_tab)
)
SELECT 
e.event_id,
sum(case when dayname(d.gen_dt) =  e.schedule_day then 1 else 0 end ) day_nos_as_run_count
FROM date_gen d, event_tab e
where 
cast(d.gen_dt as date) between e.start_date and e.end_date
group by e.event_id

DB fiddle here .

Recursive query example help from here .

Sample output -

event_id	day_nos_as_run_count
1	35
2	23
3	2
4	0

Another variant of the query -

WITH RECURSIVE 
date_gen (gen_dt) AS
(
SELECT min(start_date) from event_tab
union all
SELECT date_add(gen_dt,interval 1 day) from date_gen where gen_dt < (select max(end_date) from event_tab)
)
SELECT 
e.event_id,
count(d.gen_dt)
FROM event_tab e left join date_gen d
on ( cast(d.gen_dt as date) between e.start_date and e.end_date
and e.schedule_day = dayname(d.gen_dt))
group by e.event_id
order by e.event_id

Answer 2

Start by storing dates in date format: 03-04-2022 should be stored as 2022-04-03 (assuming that your format is day-month-year). And store into a column declared to be DATE , not VARCHAR .

Then you have the ability to use the DATEDIFF() function to get differences.