Question

我无法在我的评估中解决这个问题，需要一些帮助，

q）Michelle Bonnier预订的预订ID和入住和退房日期是什么？使用全球假日数据库。

A）

select bookingid,guestid,firstname,lastname,checkindate,checkoutdate
from guests
join bookings on guests.GuestID = bookings.GuestID
where firstname = "Michelle"
and lastname = "Bonnier";

错误代码：1066。不是唯一的表/别名：'guests'

Answer 1

由于guestid位于select列列表的两个表中，我们需要说明要使用哪一个，所以试试这个：

SELECT bookingid,
       guests.guestid,
       firstname,
       lastname,
       checkindate,
       checkoutdate
FROM   guests
       JOIN bookings
         ON guests.guestid = bookings.guestid
WHERE  firstname = "michelle"
       AND lastname = "bonnier"

Answer 2

始终尝试使用表名别名

select 
    b.bookingid,g.guestid,g.firstname,g.lastname,
    b.checkindate,b.checkoutdate
    from guests g
    join bookings b on g.GuestID = b.GuestID
    where g.firstname = "Michelle"
    and g.lastname = "Bonnier";

需要帮助连接sql

2 个答案: