MySQL - 每个人的课程总数的总价格是多少? [英] MySQL - What's the total cost in price for each person's total number of courses?

问题描述

我在计算查询中的总和时遇到问题.我敢肯定，它需要 CAST.

I am having problems working out a sum in a query. It requires a CAST I'm sure.

查询 - 我想知道每个父母的活动总费用是多少.每项活动的价格为 5.50 美元，因此有 4 项活动的人总共需要 22 美元.

The query - I want to find out how much each parents total number of activities costs. The price of each activity is $5.50, therefore someone with 4 activities would be $22 total.

它需要 3 列，分别是父名称、总活动和总成本.

It requires 3 columns which are for Parent Name, total activities, and total cost.

我无法计算出每位家长的总活动费用...

I can't work out the total cost for each parent's total activities...

请帮忙

代码

SELECT CONCAT_WS(" ", P.parent_title, P.parent_fname, P.parent_sname) AS Parent,
COUNT(A.activity_name) AS Total_Activities
FROM Activity A, Child C, Parent P, ChildActivity
WHERE P.parent_id = C.parent_id
AND C.child_id = ChildActivity.child_id
AND A.activity_id = ChildActivity.activity_id
GROUP BY Parent
ORDER BY P.parent_sname, P.parent_fname

结果示例:(实际上列出了 11 个人)

Results example: (actually lists 11 people)

  *Parent*        *Total Activities*
  MR James Dean         4

推荐答案

因为这是作业，我不能马上给你答案.这样想:您可以将数学应用于列值:)

As this is homework, I can not give you the answer right away. Think it this way: You can apply math to column values :)

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