Question

让我解释一下背景故事，老师可以设置一个在场或缺席的学生。这些学生的价值被放在一个数据库中，这个查询选择课程代码并计算某一课程中学生的百分比，但是我有点坚持做什么，文件必须转换为JSON并放入ChartJS条形图但由于某种原因我似乎无法计算出这个代码，每个类都需要计算每个百分比，因此我不能使用IN或类似的东西来计算存在整个课程而不是每节课的课程（这就是klas.code =＆＃39; $ klas＆＃39;是什么意思）有谁知道我怎么能得到1个结果但仍然能够计算每个班级的百分比分开？

谢谢。

$klassen = array("WFHBOICT.V1E", "WFHBOICT.V1F");
foreach($klassen as $klas){
//query to get data from the table
$query = ("SELECT klas.code klas, ROUND(
(
    SELECT Count(aanwezigheid) 
    FROM aanwezigheid 
    JOIN college ON aanwezigheid.Ccode = college.code  
    JOIN klas ON college.Kcode = klas.code
    WHERE klas.code = '".$klas."' AND vak.code = 'WFHBOICT.M032.16' AND college.college = '8'
    AND aanwezigheid = '1'
) 
/
(
    SELECT Count(aanwezigheid) 
    FROM aanwezigheid 
    JOIN college ON aanwezigheid.Ccode = college.code  
    JOIN klas ON college.Kcode = klas.code
    WHERE klas.code = '".$klas."' AND vak.code = 'WFHBOICT.M032.16' AND college.college = '8'
) 
* 100)
    as percentage
FROM aanwezigheid 
JOIN college ON aanwezigheid.Ccode = college.code 
JOIN klas ON college.Kcode = klas.code 
JOIN vak ON college.Vcode = vak.code 
WHERE klas.code = '".$klas."' AND vak.code = 'WFHBOICT.M032.16' AND college.college = '8'
GROUP BY klas.code");

//execute query
$result = $mysqli->query($query);

//loop through the returned data
$data = array();
foreach ($result as $row) {
$data[] = $row;
}

print json_encode($data);

结果如下：

[{"klas":"WFHBOICT.V1F","percentage":"67"}]

它必须在括号之间返回两个类而不仅仅是1 ...

Answer 1

问题来自第一个foreach循环。在它之前初始化$ data数组并在打印之前关闭第一个foreach。

$klassen = array("WFHBOICT.V1E", "WFHBOICT.V1F");

$data = array();
foreach($klassen as $klas){
    //query to get data from the table
    $query = ("SELECT klas.code klas, ROUND(
    (
        SELECT Count(aanwezigheid)
        FROM aanwezigheid
        JOIN college ON aanwezigheid.Ccode = college.code
        JOIN klas ON college.Kcode = klas.code
        WHERE klas.code = '".$klas."' AND vak.code = 'WFHBOICT.M032.16' AND college.college = '8'
        AND aanwezigheid = '1'
    )
    /
    (
        SELECT Count(aanwezigheid)
        FROM aanwezigheid
        JOIN college ON aanwezigheid.Ccode = college.code
        JOIN klas ON college.Kcode = klas.code
        WHERE klas.code = '".$klas."' AND vak.code = 'WFHBOICT.M032.16' AND college.college = '8'
    )
    * 100)
        as percentage
    FROM aanwezigheid
    JOIN college ON aanwezigheid.Ccode = college.code
    JOIN klas ON college.Kcode = klas.code
    JOIN vak ON college.Vcode = vak.code
    WHERE klas.code = '".$klas."' AND vak.code = 'WFHBOICT.M032.16' AND college.college = '8'
    GROUP BY klas.code");

    //execute query
    $result = $mysqli->query($query);

    //loop through the returned data

    foreach ($result as $row) {
        $data[] = $row;
    }
} // end first foreach
print json_encode($data);

希望它有所帮助。

MySQL查询中的Foreach循环

1 个答案: