Get all occurences of a time range between another time range

Question

I have a database that is set up with a date and a start and end time

date	start	end
2021-12-04	10:15:00	13:05:00
2021-12-04	12:18:00	15:38:00
...	...	...

This table saves times people enter or leave.

For a statistic I want to get the number of people who were clocked in for every hour

For example if I specify date "2021-12-04" the table should look like this:

hour	people
10:00-10:59	1
11:00-11:59	1
12:00-12:59	2
13:00-13:59	2
14:00-14:59	1
15:00-15:59	1

I have been trying some queries and I get tables returning the number correctly for one hour, but as soon as it comes to every hour someone has been clocked in I can't seem to find a solution that works as intended

Answer 1

checking for each hour, combining with union:

select '00:00-00:59' as hour, count(date) as people from table1
 where '00' between substr(start,1,2) and substr(end,1,2) union
select '01:00-01:59' as hour, count(date) as people from table1
 where '01' between substr(start,1,2) and substr(end,1,2) union
select '02:00-02:59' as hour, count(date) as people from table1
 where '02' between substr(start,1,2) and substr(end,1,2) union
select '03:00-03:59' as hour, count(date) as people from table1
 where '03' between substr(start,1,2) and substr(end,1,2) union
select '04:00-04:59' as hour, count(date) as people from table1
 where '04' between substr(start,1,2) and substr(end,1,2) union
select '05:00-05:59' as hour, count(date) as people from table1
 where '05' between substr(start,1,2) and substr(end,1,2) union
select '06:00-06:59' as hour, count(date) as people from table1
 where '06' between substr(start,1,2) and substr(end,1,2) union
select '07:00-07:59' as hour, count(date) as people from table1
 where '07' between substr(start,1,2) and substr(end,1,2) union
select '08:00-08:59' as hour, count(date) as people from table1
 where '08' between substr(start,1,2) and substr(end,1,2) union
select '09:00-09:59' as hour, count(date) as people from table1
 where '09' between substr(start,1,2) and substr(end,1,2) union
select '10:00-10:59' as hour, count(date) as people from table1
 where '10' between substr(start,1,2) and substr(end,1,2) union
select '11:00-11:59' as hour, count(date) as people from table1
 where '11' between substr(start,1,2) and substr(end,1,2) union
select '12:00-12:59' as hour, count(date) as people from table1
 where '12' between substr(start,1,2) and substr(end,1,2) union
select '13:00-13:59' as hour, count(date) as people from table1
 where '13' between substr(start,1,2) and substr(end,1,2) union
select '14:00-14:59' as hour, count(date) as people from table1
 where '14' between substr(start,1,2) and substr(end,1,2) union
select '15:00-15:59' as hour, count(date) as people from table1
 where '15' between substr(start,1,2) and substr(end,1,2) union
select '16:00-16:59' as hour, count(date) as people from table1
 where '16' between substr(start,1,2) and substr(end,1,2) union
select '17:00-17:59' as hour, count(date) as people from table1
 where '17' between substr(start,1,2) and substr(end,1,2) union
select '18:00-18:59' as hour, count(date) as people from table1
 where '18' between substr(start,1,2) and substr(end,1,2) union
select '19:00-19:59' as hour, count(date) as people from table1
 where '19' between substr(start,1,2) and substr(end,1,2) union
select '20:00-20:59' as hour, count(date) as people from table1
 where '20' between substr(start,1,2) and substr(end,1,2) union
select '21:00-21:59' as hour, count(date) as people from table1
 where '21' between substr(start,1,2) and substr(end,1,2) union
select '22:00-22:59' as hour, count(date) as people from table1
 where '22' between substr(start,1,2) and substr(end,1,2) union
select '23:00-23:59' as hour, count(date) as people from table1
 where '23' between substr(start,1,2) and substr(end,1,2)

dbfiddle here (MySQL 8.0.27)

Answer 2

getting concise w col1, would go with:

select substr(start, 1, 2) as hour
    , count(start) as people
from table1
group by 1
order by 1

with complete hour notation, as the example:

select concat(substr(start, 1, 2), ':00-', substr(start, 1, 2), ':59') as hour
    , count(start) as people
from table1
group by 1
order by 1

dbfiddle here (MySQL 8.0.27)