Question

我使用嵌套的while循环来检索来自2个不同表格的信息（学生，这两个表都通过主键链接的成绩 - “id”）

我希望它以下列格式输出：

Student ID "123"

 - Grade 1 for ID "123"
 - Grade 2 for ID "123"

Student ID "555"

 - Grade 1 for ID "555"
 - Grade 2 for ID "555"

Student ID "666"

 - Grade 1 for ID "666"
 - Grade 2 for ID "666"

目前输出如下：

Student ID "123"

 - Grade 1 for ID "123" 
 - Grade 2 for ID "123"
 - Grade 1 for ID "555"
 - Grade 2 for ID "555" 
 - Grade 1 for ID "666" 
 - Grade 2 for ID "666"

Student ID "555"
Student ID "666"

这是PHP代码

<?php
include ("../../php/account.php");

$dbh = mysql_connect ( $hostname, $username, $password )
                   or die ( "Unable to connect to MySQL database" );
mysql_select_db( $project );

$s = mysql_query("SELECT * FROM newstudent");
$r = mysql_query("SELECT * FROM grades");  

while($rows=mysql_fetch_array($s))
    {
    echo "Student ID: ".$rows['id']."<br/>";
    echo "First Name: ".$rows['firstname']."<br/>";
    echo "Last Name: ".$rows['lastname']."<br/>";
    echo "Email: ".$rows['email']."<br/>";
    echo "<br/>";

            while($rows=mysql_fetch_array($r))
            {
                echo "Subject: ".$rows['subject']."<br/>";
                echo "Grade One: ".$rows['gradeone']."<br/>";
                echo "Grade Two: ".$rows['gradetwo']."<br/>";
                echo "Grade Three: ".$rows['gradethree']."<br/>";
                echo "<br/>";                
            }

    }

?>

如果有人知道解决方案，请帮助我！非常感谢！

Answer 1

不要使用嵌套循环，使用JOIN在一个查询中获取所有结果：

$q = mysql_query("SELECT * FROM newstudent s
                  JOIN grades g ON s.id = g.student_id
                  ORDER BY s.id") or die (mysql_error());

$last_student = null;
while ($row = mysql_fetch_assoc($q)) {
    if ($row['id'] !== $last_student) {
        $last_student = $row['id'];
        echo "Student ID: ".$row['id']."<br/>";
        echo "First Name: ".$row['firstname']."<br/>";
        echo "Last Name: ".$row['lastname']."<br/>";
        echo "Email: ".$row['email']."<br/>";
        echo "<br/>";
    }
    echo "Subject: ".$row['subject']."<br/>";
    echo "Grade One: ".$row['gradeone']."<br/>";
    echo "Grade Two: ".$row['gradetwo']."<br/>";
    echo "Grade Three: ".$row['gradethree']."<br/>";
    echo "<br/>";                
}

Answer 2

您正在覆盖$rows变量。

Answer 3

我认为你在第二个循环中覆盖了$ rows变量。尝试使用2个不同的变量

编辑：内循环只是简单地说“打印所有成绩”，所以它与你在外循环中检查的学生没有任何关系。

肯定需要一个外键，只允许你从第一个循环中取得你正在学习的学生的成绩，就像其他人注意到的那样。

Answer 4

将您的成绩查询放入学生循环中并为其分配学生ID，也不要在循环中重新分配$rows变量。

$s = mysql_query("SELECT * FROM newstudent");


while($rows=mysql_fetch_array($s))
    {
    echo "Student ID: ".$rows['id']."<br/>";
    echo "First Name: ".$rows['firstname']."<br/>";
    echo "Last Name: ".$rows['lastname']."<br/>";
    echo "Email: ".$rows['email']."<br/>";
    echo "<br/>";

    $r = mysql_query("SELECT * FROM grades WHERE studentID = '" . $row['id'] . "'");  

            while($r=mysql_fetch_array($r))
            {
                echo "Subject: ".$r['subject']."<br/>";
                echo "Grade One: ".$r['gradeone']."<br/>";
                echo "Grade Two: ".$r['gradetwo']."<br/>";
                echo "Grade Three: ".$r['gradethree']."<br/>";
                echo "<br/>";                
            }

    }

Answer 5

试试这个

<?php
include ("../../php/account.php");

$dbh = mysql_connect ( $hostname, $username, $password )
                   or die ( "Unable to connect to MySQL database" );
mysql_select_db( $project );

$s = mysql_query("SELECT * FROM newstudent");

while($rows=mysql_fetch_array($s))
    {
    echo "Student ID: ".$rows['id']."<br/>";
    echo "First Name: ".$rows['firstname']."<br/>";
    echo "Last Name: ".$rows['lastname']."<br/>";
    echo "Email: ".$rows['email']."<br/>";
    echo "<br/>";

$r = mysql_query("SELECT * FROM grades");  

            while($rows1=mysql_fetch_array($r))
            {
                echo "Subject: ".$rows1['subject']."<br/>";
                echo "Grade One: ".$rows1['gradeone']."<br/>";
                echo "Grade Two: ".$rows1['gradetwo']."<br/>";
                echo "Grade Three: ".$rows1['gradethree']."<br/>";
                echo "<br/>";                
            }

    }

?>

这里你覆盖$rows变量。所以尝试使用不同的变量名。

在mysql数据检索中嵌套while循环

5 个答案: