sql - SQL，选择与您找到的不相等的实体

Question

SELECT HOTEL.ROOM
FROM HOTEL
  LEFT OUTER JOIN BOOKED
 ON BOOKED.ROOM = HOTEL.ROOM

 WHERE
    TO_DATE('&STARTDATE','DD-MM-YY') BETWEEN BOOKED.ARRIVALDATE 
 AND BOOKED.ARRIVALDATE + &NIGHTS

我需要帮助，我需要搜索已预订的房间并返回可用的房间。基本上，用户在查询中输入一个日期，以及他住的晚数。这是在 BOOKED 表中查找的，如果日期相等，则表示房间已预订，不应从 HOTEL.ROOM 表中选择该房间。编辑：将 RIGHT OUTER JOIN 更改为 LEFT OUTER JOIN，刚刚意识到它正在从错误的表中选择数据

Answer 1

您的日期范围内的预订：

SELECT *
FROM   BOOKED
WHERE  TO_DATE('&STARTDATE','DD-MM-YY') BETWEEN ARRIVALDATE AND ARRIVALDATE + &NIGHTS

扩展以查找HOTEL此列表中的房间，即已预订：

SELECT ROOM
FROM   HOTEL
WHERE  EXISTS (
         SELECT *
         FROM   BOOKED
         WHERE  TO_DATE('&STARTDATE','DD-MM-YY') BETWEEN ARRIVALDATE AND ARRIVALDATE + &NIGHTS
         AND    ROOM = HOTEL.ROOM
       )

而那些不在此列表中的即未预订：

SELECT ROOM
FROM   HOTEL
WHERE  NOT EXISTS (
         SELECT *
         FROM   BOOKED
         WHERE  TO_DATE('&STARTDATE','DD-MM-YY') BETWEEN ARRIVALDATE AND ARRIVALDATE + &NIGHTS
         AND    ROOM = HOTEL.ROOM
       )