如何对 MySQL 中的两个表的数学结果求和

Question

不知道该怎么办！

使用 MySQL

我需要显示特定 operatorID 的每小时总行程

因此，operatorid '2' 的总时数应该在某处显示为数字 '7'。 这个数字“7”是 TripsPerHour 的总和。

SELECT S.routeid, S.operatorid, R.routeid, S.percentage * R.frequency/100 AS TripsPerHour 
  FROM route_split S, routes R 
 WHERE R.routeid = S.routeid
   AND S.operatorid ='2';
+---------+------------+---------+--------------+
| routeid | operatorid | routeid | TripsPerHour |
+---------+------------+---------+--------------+
|       6 |          2 |       6 |       1.0000 |
|      12 |          2 |      12 |       4.0000 |
|      13 |          2 |      13 |       2.0000 |
+---------+------------+---------+--------------+
3 rows in set (0.00 sec)

Answer 1

您只需要SUM()聚合以及GROUP BY子句

SELECT S.operatorid, R.routeid, 
       SUM(S.percentage * R.frequency/100) AS TripsPerHour 
  FROM route_split S
  JOIN routes R 
    ON R.routeid = S.routeid
 GROUP BY S.operatorid, R.routeid

如果您只需要operatorid=2的值，则添加

WHERE S.operatorid = 2

在GROUP BY之前，例如

SELECT R.routeid, 
       SUM(S.percentage * R.frequency/100) AS TripsPerHour 
  FROM route_split S
  JOIN routes R 
    ON R.routeid = S.routeid
 WHERE S.operatorid = 2
 GROUP BY R.routeid

更新：您可以添加SUM() OVER () window function，前提是您的数据库版本为8.0+ ，例如

SELECT S.operatorid, R.routeid,
       SUM(S.percentage * R.frequency/100) OVER () AS Total_TripsPerHour 
  FROM route_split S
  JOIN routes R 
    ON R.routeid = S.routeid
 WHERE S.operatorid = 2

Answer 2

您还可以使用 WITH ROLLUP 选项将累积总和作为单独的行：

         SELECT  S.operatorid, R.routeid, 
       SUM(S.percentage * R.frequency/100) AS TripsPerHour ) FROM
  route_split S JOIN routes R 
    ON R.routeid = S.routeid GROUP BY S.operatorid, R.routeid WITH ROLLUP

无论您选择哪个答案，在将其投入生产之前对其进行解释。