Performance of the SELECTs - mysql

Question

I need some help performing my SELECTs. I made an SQL fiddle to show you the database.
I need to perform two queries but they didn't work fine:
First:
SELECT s.id, s.day_of_week, s.title
FROM slots s
LEFT JOIN bookings_has_slots bhs
ON s.id = bhs.slot_id
LEFT JOIN bookings b
ON bhs.booking_id = b.id
WHERE NOT EXISTS (
SELECT null
FROM bookings_has_slots bhs2
LEFT JOIN bookings b2
ON bhs2.booking_id = b2.id
WHERE b.date = '2018-01-27'
)
AND s.service_id = 3
AND s.day_of_week = DAYOFWEEK('2018-01-27');
Returns:
id day_of_week title
3 7 Après-midi (14h30 - 17h00)
But I expect:
no results, because the three slots possibilities for this day_of_week on the same date are taken.
Second:
SELECT DISTINCT b3.date AS unavailable_date
FROM bookings b3
LEFT JOIN bookings_has_slots bhs3
ON bhs3.booking_id = b3.id
LEFT JOIN slots s3
ON s3.id = bhs3.slot_id
WHERE NOT EXISTS (
SELECT null
FROM slots s
LEFT JOIN bookings_has_slots bhs
ON s.id = bhs.slot_id
LEFT JOIN bookings b
ON bhs.booking_id = b.id
WHERE NOT EXISTS (
SELECT null
FROM bookings_has_slots bhs2
LEFT JOIN bookings b2
ON bhs2.booking_id = b2.id
WHERE b.date = b2.date
)
AND s.service_id = 3
AND s.day_of_week = s3.day_of_week
);
Returns:
unavailable_date
2018-01-17
2018-01-31
2018-01-27
2018-02-03
But I expect:
unavailable_date
2018-01-17
2018-01-31
2018-01-27
Because here, there are two others slots available for the "2018-02-03" not taken by any other bookings.
Here is the sql fiddle :
http://sqlfiddle.com/#!9/89e46/9
Thanks for any help.

Answer 1

It is not the answer yet.
But Could you confirm that this will fix your 1st query:
SELECT s.id, s.day_of_week, s.title
FROM slots s
LEFT JOIN (
SELECT slot_id, booking_id
FROM bookings_has_slots bhs
INNER JOIN bookings b
ON b.id = bhs.booking_id
AND b.date = '2018-02-03'
) bhs
ON s.id = bhs.slot_id
WHERE s.day_of_week = DAYOFWEEK('2018-02-03')
AND bhs.booking_id IS NULL;
2nd query:
http://sqlfiddle.com/#!9/53a998/1
SELECT d.date unavailable_date, d.used_slots
FROM (
SELECT b.date, COUNT(b.id) used_slots
FROM bookings b
GROUP BY b.date
) d
LEFT JOIN slots s
ON s.day_of_week = DAYOFWEEK(d.date)
GROUP BY d.date
HAVING d.used_slots = COUNT(s.id);