php - 如何根据特定条件从2个表中获取数据

Question

在MySQL数据库中，我有3个表，分别称为供应商、车辆和分配表。

车辆表:

vid     vehicleName     noOfSeat     sid
========================================
13      x               10           28 
14      x               8            28
15      x               12           28
16      x               14           29 
17      x               4            29
18      x               8            30

分配的表

asgid   bid  sid  vid   did  seatBooked   assigned_start    assigned_end
============================================================================
56      15   28   13    17   3            06/01/2018 02:01  06/01/2018 04:02
57      15   28   14    15   2            06/01/2018 02:01  06/01/2018 04:02
58      15   28   15    16   3            06/01/2018 02:01  06/01/2018 04:02

在预订页面中，我需要将车辆分配到选定日期，即2018年6月1日02:01到06/01/2018年04:02

现在我想显示所选供应商的所有车辆以及车辆表中的座位数

但条件是:

将显示在我的所选日期内有可用座位数的车辆:2018年6月1日02:01至06/01/2018年04:02

例如:

必须显示以下车辆及座位数:

vid    Mp pf Seat available
===========================
13     7 ( why 7? because on my selected date 3 seats booked)
14     6 ( why 6? because on my selected date 2 seats booked)
15     9 ( why 9? because on my selected date 3 seats booked)
16     14
17     4
18     8

类似于公交车票系统。

我当前的查询:

目前，我正在使用以下查询，但它只是删除了我选择的日期中的那些视频，但这是不正确的，因为正如您所看到的，在我选择的日期几乎没有可用的座位!

// my selected date: From = '$timestart' and To = '$timeend'
foreach ($sid as $key => $value) {
    $vehicle->rowQuery("select * from vehicle where vid not in (
    select vid from assigned where assigned_start BETWEEN '$timestart' AND '$timeend' AND assigned_end BETWEEN '$timestart' AND '$timeend' ) AND sid = $value ");
}

我无法想象如何解决它:=(

非常感谢您的帮助。

Answer 1

你可以这样做:

select vehicle.*, (noOfSeat -  
  (select sum(seatBooked)
    from assigned
    where sid = 28
    and (assigned_start between '2018-01-06 02:01' and '2018-01-06 04:02' )
    and (assigned_end between '2018-01-06 02:01' and '2018-01-06 04:02')
  )) as seatsAvailable
from vehicle
having seatsAvailable > 0

http://sqlfiddle.com/#!9/c6bcb6/15