Question

为什么这个sql给出minimum字段的表为null。此外，当A在给定日期范围之间没有数据时，它会向表格提供所有rooms minimum为空

   SELECT `rooms`.*,A.`minimum`
    FROM (
        SELECT `room_id`, min(`available_rooms`) AS `minimum`
        FROM `room_bookings` 
        WHERE `date` BETWEEN '2014-02-01' and '2014-02-10' 
        GROUP BY `room_id`) as A
    INNER JOIN `rooms` on `rooms`.`room_id`=A.`room_id` 
    WHERE `rooms`.`location`='kathmandu' 
    AND `rooms`.`status`=1 
    AND A.`minimum`!=NULL

Answer 1

 SELECT `rooms`.*,A.`minimum`
    FROM (
        SELECT `room_id`, min(`available_rooms`) AS `minimum`
        FROM `room_bookings` 
        WHERE `date` BETWEEN '2014-02-01' and '2014-02-10' 
        GROUP BY `room_id` having minimum > 0) as A
    INNER JOIN `rooms` on `rooms`.`room_id`=A.`room_id` 
    WHERE `rooms`.`location`='kathmandu' 
    AND `rooms`.`status`=1

Answer 2

SELECT `rooms`.*,A.`minimum`
FROM (
    SELECT `room_id`, min(`available_rooms`) AS `minimum`
    FROM `room_bookings` 
    WHERE `date` BETWEEN '2014-02-01' and '2014-02-10' 
    GROUP BY `room_id`) as A
INNER JOIN `rooms` on `rooms`.`room_id`=A.`room_id` 
WHERE `rooms`.`location`='kathmandu' 
AND `rooms`.`status`=1 
AND A.`minimum` is not NULL

这将是正确的语法（将!=更改为is not）

Answer 3

尝试使用IS NOT NULL

SELECT `rooms`.*,A.`minimum`
    FROM (
        SELECT `room_id`, min(`available_rooms`) AS `minimum`
        FROM `room_bookings` 
        WHERE `date` BETWEEN '2014-02-01' and '2014-02-10' 
        GROUP BY `room_id`) as A
    INNER JOIN `rooms` on `rooms`.`room_id`=A.`room_id` 
    WHERE `rooms`.`location`='kathmandu' 
    AND `rooms`.`status`=1 
    AND A.`minimum` IS NOT NULL

Answer 4

试试这个：

SELECT r.*, MIN(rb.available_rooms) minimum 
FROM rooms r 
INNER JOIN room_bookings rb ON r.room_id = rb.room_id AND rb.date BETWEEN '2014-02-01' AND '2014-02-10' 
WHERE r.location = 'kathmandu' AND r.status = 1 
GROUP BY r.room_id HAVING minimum IS NOT NULL

Mysql错误不遵循哪里条件

4 个答案: