为什么此查询重复此代码中的名字和姓氏

Question

当我运行此查询时，我得到的结果是正确的，但名称和父名称在所有行中重复。我只想要一次。我举了1773身份证号来测试它。

<?


                $query = mysql_query("
                                        SELECT *
                                        FROM students,grades,subjects
                                        WHERE
                                        students.id_students = grades.id_students AND 
                                        grades.id_subjects = subjects.id_subjects AND 
                                        students.id_students = 1773 ;




                                         ");

                while ($row = mysql_fetch_assoc($query)

                    ){
                    $id_students = $row['id_students'];
                    $firstname = $row['firstname'];
                    $surename = $row['surename'];
                    $father = $row['father'];
                    $marks = $row['marks'];
                    $class = $row['class'];
                    $name = $row['name'];


                 echo "$firstname" . "$surename"; 
                 echo "$marks" ." " . "$name" ; 
                 echo "<br>";
                 echo "$class";

                    }

?>

Answer 1

在FROM子句中只使用一个表，而其他人使用JOIN。

SELECT s.*, 
       g.*, 
       su.*
FROM students s
JOIN grades g
    ON g.id_students = s.id_students
JOIN subjects su
    ON su.id_subjects = g.id_subjects
WHERE s.id_students = 1773

Answer 2

由于之前的答案将被删除，这应该是您所需要的。 $data数组与从数据库获得的数组相同。

<?php

$data = array(
    0 => array(
        'id_students' => 1,
        'firstname' => 'Fuad',
        'surename' => 'Bro',
        'father' => 'fathers name',
        'marks' => 30,
        'class' => 1,
        'name' => 'itd'
    ),

    1 => array(
        'id_students' => 1,
        'firstname' => 'Fuad',
        'surename' => 'Bro',
        'father' => 'fathers name',
        'marks' => 120,
        'class' => 1,
        'name' => 'biography'
    ),

    2 => array(
        'id_students' => 1,
        'firstname' => 'Fuad',
        'surename' => 'Bro',
        'father' => 'fathers name',
        'marks' => 120,
        'class' => 1,
        'name' => 'informatic'
    )
);

$last_name = '';

foreach ($data as $row) {
    if ($row['firstname'] != $last_name) {
        echo '<b>' . $row['firstname'] . ' ' . $row['surename'] . ' (father: ' . $row['father'] . ')</b><br>';
    }

    echo 'class: ' . $row['class'] . '<br>';
    echo 'subject name: ' . $row['name'] . '<br>';
    echo 'marks: ' . $row['marks'] . '<br><br>';

    $last_name = $row['firstname'];
}

/*
    output:

    Fuad Bro (father: fathers name) -- name and father's name just once
    class: 1
    subject name: itd
    marks: 30

    class: 1
    subject name: biography
    marks: 120

    class: 1
    subject name: informatic
    marks: 120
*/

?>