Question

房间桌＆gt;＆gt; room_id，标准

来宾表＆gt;＆gt; guest_id，访客类型

预订表＆gt;＆gt; booking_id，room_id，guest_id

我的问题是＆gt;删除已预订“豪华”客房的客人的记录。（豪华是一种标准）

请帮助？查询我是SQL的初学者。

Answer 1

我假设您只想从booking表中删除。我还假设您需要从guest表中指定某些，否则您根本不需要第三个表。

DELETE b
FROM booking b
INNER JOIN room r
    ON r.room_id = b.room_id
INNER JOIN guest g
    ON g.guest_id = b.guest_id
WHERE r.standard = 'Deluxe'
    AND g.field = ????

然而，这是MS SQL扩展。 ANSI的方法是：

DELETE FROM booking b
WHERE EXISTS (
        SELECT 1
        FROM room r
        WHERE r.room_id = b.room_id
            AND r.standard = 'Deluxe')
    AND EXISTS (
        SELECT 1
        FROM guest g
        WHERE g.guest_id = b.room_id
            AND g.field = ????)

如何从三个表中删除

1 个答案: