Question

我正在尝试查询数据库以查找以下内容。

如果客户在日期A和B之间搜索城市中的酒店，请查找并返回两个日期之间免费房间的酒店。

每种房型都会有多个房间（即A型5个房间，B型房间10个房间等），我们必须查询数据库才能找到至少有一个房间的酒店房间至少有一种免费。

这是我的表结构：

**Structure for table 'reservations'**
    reservation_id
    hotel_id
    room_id
    customer_id
    payment_id
    no_of_rooms
    check_in_date
    check_out_date
    reservation_date

    **Structure for table 'hotels'**
    hotel_id
    hotel_name
    hotel_description
    hotel_address
    hotel_location
    hotel_country
    hotel_city
    hotel_type
    hotel_stars
    hotel_image
    hotel_deleted


    **Structure for table 'rooms'**
    room_id
    hotel_id
    room_name
    max_persons
    total_rooms
    room_price
    room_image
    agent_commision
    room_facilities
    service_tax
    vat
    city_tax
    room_description
    room_deleted

这是我的疑问：

$city_search = '15';
$check_in_date = '29-03-2010';
$check_out_date = '31-03-2010';

$dateFormat_check_in = "DATE_FORMAT('$reservations.check_in_date','%d-%m-%Y')";
$dateFormat_check_out = "DATE_FORMAT('$reservations.check_out_date','%d-%m-%Y')";

$dateCheck = "$dateFormat_check_in >= '$check_in_date' AND  $dateFormat_check_out <= '$check_out_date'";

 $query = "SELECT $rooms.room_id,
                  $rooms.room_name,
                  $rooms.max_persons,
                  $rooms.room_price,
                  $hotels.hotel_id,
                  $hotels.hotel_name,
                  $hotels.hotel_stars,
                  $hotels.hotel_type
           FROM   $hotels,$rooms,$reservations
           WHERE  $hotels.hotel_city = '$city_search'
           AND    $hotels.hotel_id = $rooms.hotel_id
           AND    $hotels.hotel_deleted = '0'
           AND    $rooms.room_deleted = '0'
           AND    $rooms.total_rooms - (SELECT SUM($reservations.no_of_rooms) as tot
                                                   FROM $reservations
                                                   WHERE $dateCheck
                                                   GROUP BY $reservations.room_id) > '0'";

每间酒店的每种房型已预订的房间数量将存储在预订表中。

问题是查询根本不返回任何结果。即使我自己手动计算它也应该。

我尝试单独运行子查询，但我没有得到任何结果。而且我已经失去了相当多的头发，试图从昨天开始对这个问题进行解密。这有什么问题？或者有更好的方法来做我上面提到的吗？

编辑：编辑代码以删除错误。感谢Mark Byers。

Sample Data in reservation table

1   1   1   2   1   3   2010-03-29  2010-03-31  2010-03-17
2   1   2   3   3   8   2010-03-29  2010-03-31  2010-03-18
5   1   1   5   5   4   2010-03-29  2010-03-31  2010-03-12

子查询应该返回

Room ID : 1    Rooms Booked : 7
Room ID : 2    Rooms Booked : 8

But it does not return any value at all.... If i remove the dateCheck condition it returns
Room ID : 2    Rooms Booked : 8

Answer 1

你的问题在这里：

$rooms.total_rooms - (SELECT SUM($reservations.no_of_rooms) as tot,
                                               $rooms.room_id as id
                                               FROM $reservations,$rooms
                                               WHERE $dateCheck
                                               GROUP BY $reservations.room_id) > '0'"

您正在进行减法total_rooms - (tot, id)，其中第一个操作数是标量值，第二个是具有两列的表。删除结果集中的一列，并确保只返回一行。

您还应该使用JOIN关键字进行连接，而不是使用逗号分隔表。这样你就不会忘记添加连接条件。

你可能想要这些内容：

SELECT column1, column2, etc...
FROM   $hotels
JOIN   $rooms
ON     $hotels.hotel_id = $rooms.hotel_id
JOIN   (
    SELECT SUM($reservations.no_of_rooms) as tot,
           $rooms.room_id as id
           FROM $reservations
           JOIN $rooms
           ON ??? /* Aren't you missing something here? */
           WHERE $dateCheck
           GROUP BY $reservations.room_id
) AS T1
ON     T1.id = room_id
WHERE  $hotels.hotel_city = '$city_search'
AND    $hotels.hotel_deleted = '0'
AND    $rooms.room_deleted = '0'
AND    $rooms.total_rooms - T1.tot > '0'

MySQL - 查询有什么问题？

1 个答案: