如何对 MySQL 中两个表的数学结果求和

Question

不知道该怎么做！

使用MySQL

我需要显示特定 operatorID 每小时的总行程

所以 operatorid '2' 的总 tripsperhour 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

如果您只需要带operatorid=2的值，则添加

WHERE S.operatorid = 2

之前GROUP BY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：可以添加SUM() OVER ()window功能，前提是你的数据库版本是8.0+，比如

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 选项将累计总和作为单独的行获取：

         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，请在将其投入生产之前对其进行解释。

如何对 MySQL 中两个表的数学结果求和

How to sum a mathmatical result from two tables in MySQL

mysql

sql

group-by

sum

mysql-8.0