Minimum and Maximum Count of Overlapping Bookings - mysql

Question

I have a booking system that has multiple simultaneous bookings with a count number for each. I need to get the minimum and maximum for a specified date-range (for a day, in this case). I found some good code here, which works great in the test. But in my implementation, it fails in this particular instance:
It does not count bookings that start prior to the query-range and end within the query-range.
How do I fix this?
Here is an example:
This booking exists with these properties:
listings (an ID that multiple bookings can have, but only one in this case): 2f23f23f
date_start: 2016-01-15 08:00:00
date_end: 2016-01-17 08:00:00
state: active
count: 1
Result:
min_count: 0
max_count: 0
It should return:
min_count: 0
max_count: 1
If we query the very same, but with date range 2016-01-16 00:00:00 - 2016-01-16 23:59:59, it returns the correct answer:
min_count: 1
max_count: 1
Here is the MYSQL:
SELECT
MAX(simultaneous) AS max_count,
MIN(simultaneous) AS min_count
FROM (
SELECT IFNULL(SUM(
(
CASE WHEN (
listings = '2f23f23f'
AND
(state = 'active')
)
THEN count
ELSE 0
END
)
),0) AS simultaneous
FROM bookings RIGHT JOIN (
SELECT date_start AS boundary
FROM bookings
WHERE date_start BETWEEN '2016-01-17 00:00:00' AND '2016-01-17 23:59:59'
UNION
SELECT date_end
FROM bookings
WHERE date_end BETWEEN '2016-01-17 00:00:00' AND '2016-01-17 23:59:59'
UNION
SELECT MAX(boundary)
FROM (
SELECT MAX(date_start) AS boundary
FROM bookings
WHERE date_start <= '2016-01-17 00:00:00'
UNION ALL
SELECT MAX(date_end)
FROM bookings
WHERE date_end <= '2016-01-17 23:59:59'
) t
) t ON date_start <= boundary AND boundary < date_end
LEFT OUTER JOIN cart ON cart_bookings = id
GROUP BY boundary
) t

Answer 1

Whew, ok, here's the answer. The original evidently wasn't complete. It needed to include the start/end dates of the time-range being requested.
UNION
SELECT :date_start
UNION
SELECT :date_end
Complete code:
SELECT
MAX(simultaneous) AS max_count,
MIN(simultaneous) AS min_count
FROM (
SELECT IFNULL(SUM(
(
CASE WHEN (
listings = '2f23f23f'
AND
(state = 'active')
)
THEN count
ELSE 0
END
)
),0) AS simultaneous
FROM bookings RIGHT JOIN (
SELECT date_start AS boundary
FROM bookings
WHERE date_start BETWEEN '2016-01-17 00:00:00' AND '2016-01-17 23:59:59'
UNION
SELECT date_end
FROM bookings
WHERE date_end BETWEEN '2016-01-17 00:00:00' AND '2016-01-17 23:59:59'
UNION
SELECT MAX(boundary)
FROM (
SELECT MAX(date_start) AS boundary
FROM bookings
WHERE date_start <= '2016-01-17 00:00:00'
UNION ALL
SELECT MAX(date_end)
FROM bookings
WHERE date_end <= '2016-01-17 23:59:59'
) t
UNION
SELECT :date_start
UNION
SELECT :date_end
) t ON date_start <= boundary AND boundary < date_end
LEFT OUTER JOIN cart ON cart_bookings = id
GROUP BY boundary
) t