Question

我想通过book_id加入5个表。我试过了：

 SELECT booked_room_info . * , booking_info . * , hotel_info.name as
 hotelname,hotel_info.address as hoteladdress,hotel_info.contact as
 hotelcontact , personal_info . *,room_registration.room_name as
 roomname,room_registration.price as roomprice,room_registration.price as
 roomprice,room_registration.description as
 roomdescription,room_registration.image as roomimage
    FROM booked_room_info
    JOIN booking_info ON booking_info.booking_id = booked_room_info.booking_id
    JOIN hotel_info ON hotel_info.id = booking_info.hotel_id
    JOIN personal_info ON personal_info.booking_id = booked_room_info.booking_id
    JOIN room_registration ON room_registration.hotel_id = booking_info.hotel_id
    WHERE booked_room_info.booking_id= 1

但是如果我在booking_id = 1上预订了2个，但它获得了10个结果。我想我应该做一个if条件。如果(booked.room_type && book_info.hotel_id)相同，那么只从room_registration获取行，但我怎样才能完成它。

booked_room_info
------
id | booking_id | room_type | check_in | check_out
1  |  1         | delux     | 2015/1/2 | 2015/1/5
booking_info
---------
id | booking_id | hotel_id | user_id 
 1 |  1         |  2       |  1 

hotel_info
----------
id |   name    | address | user_id
 2 |palm hotel | newyork | 1

personal_info 
-------------
id  |full_name    | address | nationality | booking_id
 1  | sushil stha | new york | smth       |  1

room_registration
-----------------
id | room_name | price | image   | hotel_id  | user_id
 1 |  delux    | 1000  |room.jpg |  2        |  1

Answer 1

您上次加入时出错：

JOIN room_registration ON room_registration.hotel_id = booking_info.hotel_id

您正在使用hotel_id列加入这些表格。 room_registration表中可能有5行hotel_id=2。因此，在加入后，您会收到2*5=10行而不是预期的行。

所以你应该以不同的方式加入这张桌子如果您希望从room_registration表格中加入一行，那么您必须指定更精确的连接条件。

要正确加入room_registration表，您可以将room_registration_id列添加到booking_info表。然后你可以使用：

加入

JOIN room_registration ON room_registration.id = booking_info.room_registration_id

Answer 2

使用INNER JOIN，删除重复字段。

SELECT 
bri.*, 
bi.*, 
hi.name AS hotelname, hi.address as hoteladdress, hi.contact AS hotelcontact, 
pi.*, 
rr.room_name AS roomname, rr.price AS roomprice, rr.description AS roomdescription, rr.image AS roomimage
FROM booked_room_info bri
INNER JOIN booking_info bi ON bri.booking_id = bi.booking_id
INNER JOIN hotel_info hi ON bi.hotel_id  = hi.id
INNER JOIN personal_info pi ON bri.booking_id = pi.booking_id
INNER JOIN room_registration rr ON bi.hotel_id = rr.hotel_id
WHERE bri.booking_id = 1

如何使用IF条件连接5个表

2 个答案: