Question

我想从数据库中获取所有teacher_id，然后在另一个sql中循环每个teacher_id。

我得到这样的teacher_id：

$teachersql = "SELECT DISTINCT teacher_name, teacher_id FROM `dancers` WHERE school = '$ownerSchool'";
        $teacherres = mysqli_query($con,$teachersql);

        while($chartData2=mysqli_fetch_array($teacherres)){
             $teacher_Id = $chartData2['teacher_id'];


            }
        ?>

我得到了ID的数组。现在，我想使用该数组，然后使用每个ID执行另一个sql，这样我就可以计算出每个老师有多少个初学者。

我得到的是

Teacher     |   Level
Liv         |   Beginner
Liv         |   Beginner
Liv         |   Novice
Tee         |   Open champ
Mike        |   Major
Liv         |   Beginner

但是我想要的是对每个老师进行一次sql调用，然后计算该老师的初学者人数。

所以如果我做$teachersql2 = "SELECT * FROM舞蹈演员WHERE teacher_id = '$teacher_Id'";

我希望它为$teacher_id array中的每个老师ID打电话。并且正在寻找这个结果：

Teacher     |   Count
Liv         |   3 Beginner, 1 Novice
Tee         |   1 Open champ
Mike        |   1 Major

这样，我可以将count（3）放入变量，将（1）放入变量以在其他位置使用。

完整代码：

// GET TEACHERS


        $teachersql = "SELECT DISTINCT teacher_name, teacher_id FROM `dancers` WHERE school = '$ownerSchool'";
        $teacherres = mysqli_query($con,$teachersql);

        while($chartData2=mysqli_fetch_array($teacherres)){
             $teacher_Id = $chartData2['teacher_id'];
             $teacherNames = $chartData2['teacher_name'];
             $teacherNames = str_replace(' ', '', $teacherNames);
             $teacherNames = str_replace('.', '', $teacherNames);
             $var2 = 'data';
             $newVar2 = $var2 . $teacher_Id . $teacherNames;

            $teachersql2 = "SELECT * FROM `dancers` WHERE teacher_id = '$teacher_Id'";
            $teacherres2 = mysqli_query($con,$teachersql2);
            while($chartData3=mysqli_fetch_array($teacherres2)){
                $preB_percent = $chartData3['current_lvl'];
        ?>
        //CHART BY TEACHERS
        var <?php echo $newVar2; ?> = google.visualization.arrayToDataTable([
            ['<? $total_students; ?> Pre-Beginners', '<?php $lvl_beginner; ?> Beginners', '<?php $lvl_advanced; ?> Advanced Beginners', '<?php echo $lvl_novice; ?> Novices', '<?php echo $lvl_prizeWinner; ?> Prize Winners', '<?php $lvl_prelim; ?> Prelim Champions', '<?php echo $lvl_open; ?> Open Champions', '<?php echo $lvl_major; ?> Majors'],
            ['<?php echo $preB_percent; ?>', '<?php echo $beginner_percent; ?>', '<?php echo $advanced_percent; ?>', '<?php echo $novice_percent; ?>', '<?php echo $prizeWinner_percent; ?>', '<?php echo $prelim_percent; ?>', '<?php echo $open_percent; ?>', '<?php echo $major_percent; ?>']
        ]);

        <?php }} ?>

也许有更好的方法可以做到这一点。但是我真的需要帮助，我已经待了好几天了。希望我的问题有意义

Answer 1

您可以使用group by将两个查询合并为一个查询，例如SQL波纹管：

SELECT teacher_name, current_lvl, count(teacher_id) as count
FROM dancers
WHERE school = '$ownerSchool'  
GROUP BY current_lvl, teacher_id
ORDER BY teacher_name ASC

产生的结果将类似于以下模式：

Teacher     |  Level        | Count
Liv         |  Beginner     |   3
Liv         |  Novice       |   1
Tee         |  Open champ   |   1
Mike        |  major        |   1

您可以使用php代码合并结果以生成数据图表

$results = mysqli_query($con, $teacher_sql);

$last_teacher_name = "";
$current_index;
$chart_data = [];

while($row = mysqli_fetch_array($results)) {

    $teacher_name = $row["teacher_name"];
    $current_lvl = $row["current_lvl"];
    $total_dancers = $row["count"];

    if ($teacher_name != $last_teacher_name ) {
        $chart_data += ["teacher_name" => $teacher_name];
        $last_teacher_name = $teacher_name;
        $current_index = count($chart_data) - 1;
    }

    $chart_data[$current_index]["current_lvl"] = $current_lvl;
    $chart_data[$current_index]["count"] = $total_dancers;
}

注意： 注意@Dharman插入的sql注入很重要

使用Prepared Statements来防止此问题的使用

如何将变量循环到sql调用

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