`` $query = "SELECT t1.ID,t1.student_id, t1.Subject, t1.1st_Grading, t1.2nd_Grading, t1.3rd_Grading, t1.4th_Grading, t1.Status, SUM(t1.1st_Grading + t1.2nd_Grading + t1.3rd_Grading + t1.4th_Grading) / 4 as Average FROM grading_system t1 LEFT JOIN studentdata t2 ON t1.student_Id = t2.ID GROUP BY t1.ID ";
这是这段代码的结果，如果你看到url中的红色箭头，它是一个学生# 1，里面还包括学生# 2项 
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当用户点击学生 ID 为 1 的链接时，将获取该链接中的参数 id，然后在 PHP 中使用 global 变量 $_GET['id'] 来查询数据库，并在查询中使用 WHERE 子句。
// Get the student ID from the URL parameter $studentId = isset($_GET['id']) ? $_GET['id'] : null; // Prepare the SQL query with the WHERE clause to fetch the specific student's data $query = "SELECT t1.ID, t1.student_id, t1.Subject, t1.1st_Grading, t1.2nd_Grading, t1.3rd_Grading, t1.4th_Grading, t1.Status, SUM(t1.1st_Grading + t1.2nd_Grading + t1.3rd_Grading + t1.4th_Grading) / 4 as Average FROM grading_system t1 LEFT JOIN studentdata t2 ON t1.student_Id = t2.ID WHERE t1.student_id = $studentId GROUP BY t1.ID";