Question

我有以下代码，其中，我根据用户获得练习的ID和练习的总时间。

SELECT practice.id, SUM(practice.duration) as dur 
FROM trainingPractice 
INNER JOIN training 
ON trainingPractice.trainingId = training.id
INNER JOIN trainingStudent 
ON trainingPractice.trainingId = trainingStudent.trainingId
INNER JOIN practice 
ON trainingPractice.practiceId = practice.id
WHERE trainingStudent.studentId = '$id'
GROUP BY practice.id

但是，我是否有可能获得该练习的总时间？当然在同一个查询中。

示例：

 id   |   dur   |   durTotal   |
-------------------------------
 23       45          240

用户在240分钟内练习23分钟45分钟

Answer 1

只需添加另一个子查询。

Marshal.load

Answer 2

我不确定这是否会完全正常，因为我不知道您的确切表结构和关系，我也更习惯MS SQL Server而不是MySQL，但它应该指向正确的方向：

SELECT practice.id,
    SUM(practice.duration) as durTotal,
    SUM(CASE trainingStudent.studentId WHEN '$id' THEN practice.duration ELSE 0 END) as dur 
FROM trainingPractice 
INNER JOIN training 
ON trainingPractice.trainingId = training.id
INNER JOIN trainingStudent 
ON trainingPractice.trainingId = trainingStudent.trainingId
INNER JOIN practice 
ON trainingPractice.practiceId = practice.id
GROUP BY practice.id

两个不同的变量，但一个用于总计，一个用于特定用户

2 个答案: