SQL更新语句

我有两张桌子-客房和客房预订，包括：

                       room
rCode | rName | building | capacity | disabledAccess
Text  | Text  |   Text   |  Number  |     Yes/No

                                roomBooking
bookingID | roomCode | moduleCode | dayReq | timeReq | semester | classSize
  Number  |   Text   |    Text    |  Text  | Day/Time|  Number  |  Number

我想写一个UPDATE语句来更新任何时候都没有预订的房间-结果显示在下面的SELECT查询中

 SELECT rCode, disabledAccess
 FROM room
 LEFT JOIN roomBooking
 ON room.rCode = roomBooking.roomCode
 WHERE roombooking.roomCode IS NULL;

---

如何将其更改为UPDATE语句？

使用左连接并仅返回不符合连接条件的房间

SELECT rCode, disabledAccess
 FROM room
 LEFT JOIN roomBooking
 ON room.rCode = roomBooking.roomCode
 WHERE roomBooking.roomCode is NULL

---

您应该使用左连接并测试NULL来显示不匹配的行

SELECT rCode, disabledAccess
FROM room
LEFT JOIN roomBooking
ON room.Code = roomBooking.roomCode
WHERE roombooking.roomCode IS NULL

---

您可以沿着这条路径走，但需要一个

左连接

，然后进行比较以确定哪些行不匹配。在这种情况下，不需要

exists

子句：

SELECT r.rCode, r.disabledAccess
FROM room as r LEFT JOIN
     roomBooking as rb
     ON r.rCode = rb.roomCode
WHERE rb.roomCode IS NULL;

编辑：

MS Access接受

更新的
连接
语法：

UPDATE room
    SET <foo> = <bar>
    FROM room LEFT JOIN
         roomBooking
         ON room.rCode = roomBooking.roomCode
    WHERE roomBooking.roomCode IS NULL;

更新室
集合=
从房间左侧连接
客房预订
ON room.rCode=roomBooking.roomCode
其中roomBooking.roomCode为空；

您是否不清楚要更新哪些列。
使用
左连接
并检查右侧（
roomBooking
）
是否为空
我想将disabledAccess更新为yes（设置disabledAccess=1），但当我运行此操作时，我收到一条语法错误消息，该SQL对我有效：）更新room LEFT加入roomBooking ON room.rCode=roomBooking.roomCode SET disabledAccess=1，其中roomBooking.roomCode为NULL；