MySQL-查询出了什么问题？

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和日期B之间搜索城市中的酒店，请查找并返回两个日期之间有空房间的酒店。

每种房型将有一个以上的房间（即A型有5个房间，B型有10个房间，等等），我们必须查询数据库以仅找到在其中至少有一个空房间的那些酒店。至少一种类型。

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

这是我的查询：

$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'";

每种酒店在每种房型中已经预订的房间数将存储在预订表中。

问题是查询根本不返回任何结果。 即使我自己手动计算也应该如此。

我尝试单独运行子查询，但没有得到任何结果。 而且从昨天开始尝试调试该查询时，我已经失去了很多精力。 这怎么了 还是有更好的方法来做我上面提到的事情？

编辑：已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

您的问题在这里：

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

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

您还应该使用JOIN关键字进行联接，而不是用逗号分隔表。 这样，您就不会忘记添加连接条件。

您可能需要遵循以下原则：

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'