Select all available items in a specific period - mysql

Question

So I have 2 tables caring and client, like this
client {
id,
name
}
caring {
id,
startDate,
endDate,
clientId
}
I need to get all clients that have at least one day available between two provided dates, you can see my screenshot as reference.
In screenshot I have two clients, and I need to return both of them. As you can see, the first client have three free days (21.5.-23.5.) between provided period (16.5.-29.5.) and the second client have not any caring periods.
So far i have tried something like this
SELECT * FROM client cl
WHERE cl.id NOT IN (SELECT clientId FROM caring
WHERE endDate >= CURDATE() AND endDate <= DATE_ADD(CURDATE(), INTERVAL 14 DAY))
This one return only clients that don't have carings at all. That is partially what I need because this query don't cover first client from my screenshot. Then I tried query bellow.
SELECT ca.startDate, ca.endDate, cl.firstName, cl.lastName
FROM caring ca
LEFT JOIN client cl on cl.id = ca.clientId
WHERE ca.startDate NOT IN (
SELECT endDate
FROM caring
) AND ca.startDate <= '2017-05-29' AND ca.endDate >= '2017-05-16'
But im not getting desired results.
Any idea how I can achieve this, thx in advance!

Answer 1

Select carings in period of interest and limit start/end dates to this period, respectively. This limitation will allow for easier counting of "booked" i.e. not-free days later on.
SELECT ca.id,
-- Limit start/end dates to period of interest, respectively
GREATEST (ca.startDate, '2017-05-16') AS `effectiveStartDate`,
LEAST (ca.endDate, '2017-05-29') AS `effectiveEndDate`,
ca.clientId
FROM carings ca
WHERE ca.startDate <= '2017-05-29' AND ca.endDate >= '2017-05-16';
Next, count booked days:
DATEDIFF (DATE_ADD (LEAST (ca.endDate, '2017-05-29'), INTERVAL 1 DAY),
GREATEST (ca.startDate, '2017-05-16'))
AS `effectiveDays`
Finally, filter out clients that are booked over the whole period. This is done by comparing
the sum of booked days per client (GROUP BY) to
the number of days of the whole period (HAVING sumDays < DATEDIFF(...)).
As you want also clients that are not booked at all over the whole period, I would suggest to start from the clients table and "just" LEFT JOIN the (effective) carings:
SELECT cl.id, cl.name, IFNULL (SUM (eca.effectiveDays), 0) AS `sumDays`
FROM clients cl
LEFT JOIN
(SELECT ca.id,
-- Limit start/end dates to period of interest, respectively
GREATEST (ca.startDate, '2017-05-16') AS `effectiveStartDate`,
LEAST (ca.endDate, '2017-05-29') AS `effectiveEndDate`,
DATEDIFF (
DATE_ADD (LEAST (ca.endDate, '2017-05-29'), INTERVAL 1 DAY),
GREATEST (ca.startDate, '2017-05-16'))
AS `effectiveDays`,
ca.clientId
FROM carings ca
WHERE ca.startDate <= '2017-05-29' AND ca.endDate >= '2017-05-16')
eca -- effectiveCarings
ON eca.clientId = cl.id
GROUP BY cl.id, cl.name
HAVING sumDays <
DATEDIFF (DATE_ADD ('2017-05-29', INTERVAL 1 DAY), '2017-05-16')
ORDER BY cl.id;
See also http://sqlfiddle.com/#!9/1038b9/19

Answer 2

Select clients whose endDate happens before the last day of your provided period and there's a gap between endDate and startDate during the specified period.
SELECT * FROM client FULL OUTER JOIN caring ON client.id = caring.clientId WHERE endDate <= '2017-05-28' AND DATEDIFF(day, startDate, endDate) > DATEDIFF(day, '2017-05-16' , endDate);