sql中的sum语句

Question

=======================================
Flight   SeatType   Price   GrandTotal
=======================================
F36712   Business   $480
         Economy    $375
         First      $450       ?

F12314   Business   $100
         Economy    $200
         First      $300       ?

我试过这个SQL：

$sql = "SELECT FlightID,SeatType, sum(SeatPrice)Total
                  FROM seat 
                  WHERE SeatAvailable = 'Yes'
                  GROUP BY FlightID,SeatType, SeatPrice";

我能否知道如何计算总计（每次航班的业务，经济和头等舱的总和）？

Answer 1

您的查询版本在group by SeatPrice中具有SeatPrice 。 这意味着您将获得每个座位价格的单独一行。 我假设您想获取每个SeatType组的SeatType ：

SELECT FlightID,SeatType, sum(SeatPrice) as Total
FROM seat 
WHERE SeatAvailable = 'Yes'
GROUP BY FlightID, SeatType with rollup;

但是，这并未将总计放在单独的列中。 再次，大多数版本的SQL支持窗口都可以执行此操作：

SELECT FlightID,SeatType, sum(SeatPrice) as Total,
       sum(sum(SeatPrice)) over (partition by FlightId)
FROM seat 
WHERE SeatAvailable = 'Yes'
GROUP BY FlightID, SeatType;

编辑：

MySQL不支持窗口功能。 您可以对联接和聚合执行相同的操作：

SELECT s.FlightID, s.SeatType, sum(s.SeatPrice) as Total, f.GrandTotal
FROM seat s join
     (select FlightId, sum(SeatPrice) as GrandTotal
      from seat
      where SeatAvailable = 'Yes'
      group by FlightId
     ) f
     on s.FlightId = f.FlightId
WHERE s.SeatAvailable = 'Yes'
GROUP BY s.FlightID, s.SeatType;

Answer 2

既然如此，您需要将GrandTotal设为您无法在GROUP BY中使用SeatType的每个航班的所有商务，经济舱和头等舱座位的总和。

$sql = "SELECT FlightID, SUM(SeatPrice) AS Total
        FROM seat 
        WHERE SeatAvailable = 'Yes'
        GROUP BY FlightID";