Mysql 使用条件语句选择

输出：

-------------------------------
StudentID| SubCode  | Marks   | 
-------------------------------
B016124  |   112    |     89  |    
B016124  |   114    |     91  |     
B016124  |   116    |     99  |       
-------------------------------
B016129  |   112    |     78  |    
B016129  |   114    |     88  |     
B016129  |   116    |      0  |    

如何计算上述select语句中的TotalMarks，其中 如果学生没有参加考试，则TotalMarks=0（子代码=116）

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否则，请使用PractEx112（子代码=112）、PractEx114（子代码=114）和ExamMrks116（子代码=116）之和。一个选项是将这些结果放入子查询中，然后使用

case

：

            SubCode=112   SubCode=114  SubCode=116  tot of 112+114 |Tot 112+114+116
-----------------------------------------------------------------------------------
StudentID  | PractEx112  | PractEx114| TotalPract    |ExamMrks116  | TotalMarks   |
-----------------------------------------------------------------------------------
B016124    |       89    |     91    |      180      |    90       |      270     |
-----------------------------------------------------------------------------------
B016129    |       78    |     88    |      166      |     0       |        0     |
-----------------------------------------------------------------------------------


Select StudentID,
        , sum(CASE WHEN SubCode = 112 THEN Marks END) AS PractEx112
        , sum(CASE WHEN SubCode = 114 THEN Marks END) AS PractEx114
        , sum(CASE WHEN SubCode IN(112,114) THEN Marks END) AS TotalPract
        , sum(CASE WHEN SubCode = 116 THEN Marks END) AS ExamMrks116

FROM STUDENTS
GROUP BY StudentID

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请格式化你的问题。我理解你的输入和预期输出，但我无法理解你对所需逻辑的陈述。我如何设置问题的格式？我有图像或文本格式的整个问题。我需要计算总分，即PractEx112+PractEx114+ExamMrks116。如果学生未使用ExamMrks116，则他们的粒子不会添加到TotalMarks，并且TotalMarks=0，只有在ExamMrks116列中输入了标记时才会添加。这不起作用，因为PractEx112、PractEx114、PractEx116和TotalTotalTotal不是学生表中使用的变量

select StudentID, PractEx112, PractEx114, PractEx116, 
    case when PractEx116 = 0 then 0 else TotalOverall end total
from (
    select StudentID, 
        sum(case when SubCode = 112 then Marks end) AS PractEx112 , 
        sum(case when SubCode = 114 then Marks end) AS PractEx114 , 
        sum(case when SubCode in (112,114) then Marks end) AS TotalPract , 
        sum(case when SubCode = 116 then Marks end) AS ExamMrks116
        sum(case when SubCode in (112,114,116) then Marks end) AS TotalOverall
    from students 
    group by StudentID
) t