MySQL查询问题：类似系统的保留

Question

房间可能有或没有保留。 保留时间为（日期）至直到（日期）。 人员按日期搜索房间：from_field和till_field。 尝试查找是否有房间。

SELECT rooms.* FROM rooms
LEFT JOIN reservations ON reservations.room_id = rooms.id
WHERE ( reservations.from > till_field OR reservations.till < from_field )

问题：如果单个预订成功，则查询似乎有可用的空间，即使另一个预订占据了该位置。

Answer 1

如何检索完全没有保留的房间：

如果没有保留，则查询=>返回的没有reservations行，您还必须检查该行（ reservations.room_id IS NULL ）：

SELECT rooms.* FROM rooms
LEFT JOIN reservations ON reservations.room_id = rooms.id
WHERE reservations.room_id IS NULL -- if there is no reservations
      OR reservations.from > till_field
      OR reservations.till < from_field

但是要真正获得想要的东西，您必须检查没有预订的房间：

• fromDate or tillDate between from_field and till_field

OR

• fromDate < from_field and tillDate > till_field

SELECT rooms.*
  FROM rooms
 WHERE NOT EXISTS (SELECT NULL
                   FROM reservations 
                  WHERE reservations.room_id = rooms.id
                    AND ((
                          reservations.from BETWEEN from_field AND till_field
                          OR
                          reservations.till BETWEEN from_field AND till_field
                         )
                        OR
                         (
                          reservations.from < from_field
                          AND reservations.till > till_field
                         )
                        )
                  )