mysql - 将列值拆分为多个列值(生成学生出勤报告)

Question

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Answer 1

要回答您的问题，请引用以下内容

CREATE TABLE student (studentid INTEGER , attendanceDate VARCHAR(20));

我创建了一个表并在表中插入了以下数据

studentid  attendanceDate
---------  --------------
        1  AA            
        2  AP            
        3  PA            
        4  PP 

如果您将运行以下查询，您将获得所需的输出

SELECT T.studentid ,T.foreNoon,T.afterNoon, IF(T.forenoon=T.afternoon && T.forenoon ='A', '100%' ,
    IF(T.forenoon=T.afternoon && T.forenoon ='P' , '0%' ,'50%'))     AS percentage
 FROM (
 SELECT studentid, SUBSTRING(attendanceDate,1,1) AS foreNoon,SUBSTRING(attendanceDate,2,1) AS afterNoon  FROM student )T

如果您运行上面的查询，您将得到如下所示的输出

studentid  foreNoon  afterNoon  percentage
---------  --------  ---------  ----------
    1  A         A          100%      
    2  A         P          50%       
    3  P         A          50%       
    4  P         P          0%        

使用MYSQL的substring方式即可解决