MYSQL 过滤多个日期作为数组

Question

下面的代码可以正常工作，但现在我想像这样添加多个日期:

reservationStartDate = 2018-07-16, 2018-07-17

SELECT 
    *,
    SUM(IF(reservationId IS NULL,
        0,
        reservationStartDate = '2018-07-17')) AS ConflictingReservations
FROM
    units
        LEFT JOIN
    reservations ON (unitsId = reservationSpace)
WHERE
    unitsType = 'room1'
GROUP BY unitsId
HAVING ConflictingReservations = 0;

Answer 1

我会这样做:

SELECT u.unit_id,
       SUM(r.reservationStartDate IN ('2018-07-17')) AS ConflictingReservations
FROM units u LEFT JOIN
     reservations r
     ON u.unitsId = r.reservationSpace
WHERE u.unitsType = 'room1'
GROUP BY u.unitsId
HAVING ConflictingReservations = 0;

或者，更简单地说:

SELECT u.*
FROM units u LEFT JOIN
     reservations r
     ON u.unitsId = r.reservationSpace AND
        r.reservationStartDate in ( . . . )
WHERE u.unitsType = 'room1' AND r.reservationSpace IS NULL;

根本不需要 GROUP BY，因为您没有使用计数。