Php Mysql如何将多个Where子句添加到单个表中

我的表上有这个查询，它返回下面给出的表

SELECT sub.Subject_Name, count(sa.Attendance) AS Lectures_Attended FROM student_attendance sa
            INNER JOIN TeacherSubjects ts on (sa.TeacherSubject_ID = ts.TeacherSubject_ID)
            INNER JOIN Subjects sub on(ts.Subject_ID = sub.Subject_ID)
            where sa.Student_ID = 1 AND sub.Semester = '8th-Semester' AND sa.Attendance=1
            GROUP by sa.TeacherSubject_ID
UNION ALL

SELECT sub.Subject_Name, count(sa.Attendance) AS Total_Lectures FROM student_attendance sa
            INNER JOIN TeacherSubjects ts on (sa.TeacherSubject_ID = ts.TeacherSubject_ID)
            INNER JOIN Subjects sub on(ts.Subject_ID = sub.Subject_ID)
            where sa.Student_ID = 1 AND sub.Semester = '8th-Semester'
            GROUP by sa.TeacherSubject_ID

SubjectName LecturesAttended                                                     
    Php           2                                                             
    Php           3

现在我不需要第二行，即Php | 3

我需要这张桌子像这样展示

SubjectName  LecturesAttended  TotalLectures                              
   Php             2               3

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您只需将查询减少到：

SELECT 
    sub.Subject_Name, 
    COUNT(IF(sa.Attendance=1,1,NULL)) AS Lectures_Attended,
    COUNT(*) Total_Lectures
FROM student_attendance sa INNER JOIN TeacherSubjects ts ON (sa.TeacherSubject_ID = ts.TeacherSubject_ID)
INNER JOIN Subjects sub ON (ts.Subject_ID = sub.Subject_ID)
WHERE sa.Student_ID = 1 AND sub.Semester = '8th-Semester'
GROUP by sa.TeacherSubject_ID;

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查看mysql中if函数的工作原理。

听起来您已经熟悉要查找的关键字了<代码>其中。你看过如何使用它的例子吗？你试过什么吗？你试过什么，什么不起作用？看：是的，我试过很多次了，看我想在一个单独的专栏里记录参加的讲座的次数，即（2）和全部讲座的次数，即（3）感谢真主保佑你，欢迎你@MansoorKhanAadeez，但我不是穆斯林，不相信真主。