Question

我必须显示学生的“约翰”信息。

约翰的信息表-学生

id  | Roll | name  | class  | year 
==================================
1   |    1 | john  |     7  | 2

约翰的马克表-马克

id  |   std_id  |   sub_id  |   th  |   pr
===========================================
1   |   1       |   1       |   60  |   20
2   |   1       |   2       |   55  |   18

约翰的教育年表-年

id  |   title
=============
1   |   2017
2   |   2018

约翰的课堂表-课堂

id  |   title
=============
7   |   Seven
8   |   Eight

约翰的主题表-主题

id  |   title
=============
1   |   Science
2   |   Math

现在我的要求如下

Name: John
Class: Seven
Year: 2018
Science: 60 (TH)
Math: 55 (TH)

但是，这里得到重复的结果。我得到john的信息，该信息重复计算了该学生的mark表中的总行。

Name: John
Class: Seven
Year: 2018
Science: 60 (TH)

Name: John
Class: Seven
Year: 2018
Math: 55 (TH)

我尝试使用GROUP BY到std.id，以防止重复，但它仅显示标记表的第一行。在这里，只有科学标记显示出来。

$result=$con->prepare(
    "SELECT
        student.id, student.en_name AS name, student.class, 
        class.title AS class, 
        year.title AS year,
        subject.title AS sub,

        mark.sub_id,
        mark.th,
        mark.pr

        FROM student

        JOIN year ON year.id = student.year 
        JOIN class ON class.id = student.class 
        JOIN mark ON mark.std_id = student.id
        INNER JOIN subject ON subject.id = mark.sub_id
        WHERE student.id=:id;"
) or die($con->error);

    $result->bindParam(':id',$_POST['std']);
    $result->execute();
    while($row=$result->fetch(PDO::FETCH_ASSOC)){
        $name=$row['name'];
        $class=$row['class'];
        $sub=$row['sub'];
        $year=$row['year'];
        $th=$row['th'];
        $pr=$row['pr']; echo" 
        <article id='blg_half'>
            <article class='left'>
                Name: $name<br/>
                Class: $class<br/>
                Year: $year<br/>
                $sub : $th(th)
            </article>
        </article>";
    }

Answer 1

尝试使用内部联接，无需根据您的问题进行分组

    SELECT
        student.roll, student.name, student.address, student.img, student.class, student.section,
        class.title AS class, 
        section.title AS section, 
        year.title AS year,
        mark.id, mark.th, mark.pr
        FROM student 
        inner JOIN year ON year.id = student.year 
        inner class ON class.id = student.class 
        inner JOIN section ON section.id = student.section
        inner JOIN mark ON mark.std_id = student.id
group by student.roll, student.name, student.address, student.img, student.class, student.section,
        class.title AS class, 
        section.title AS section, 
        year.title AS year,
        mark.id, mark.th, mark.pr

Answer 2

根据您更新的问题，您实际上需要GROUP_CONCAT才能产生结果：

SELECT
    student.id, 
    student.roll, student.name, student.address, student.img, 
    class.title AS class,
    subject.title AS sub,
    `year`.title AS yr,
    GROUP_CONCAT(mark.th) AS th,
    GROUP_CONCAT(mark.pr) AS pr
FROM student 
JOIN `year` ON `year`.id = student.`year` 
JOIN class ON class.id = student.class 
LEFT JOIN mark ON mark.std_id = student.id
LEFT JOIN subject ON subject.id = mark.sub_id
WHERE student.id = :id 
GROUP BY student.id

MySQL应该可以使用上述SQL，但是标准SQL应该按SELECT中除GROUP_CONCAT（）之外的所有字段进行分组

此外，当选择mark.id时，您不能按...分组-这毫无意义

Answer 3

尝试与标记表左连接：

SELECT 
student.roll, student.name, student.address, student.img, student.class, student.section,
class.title AS class, 
section.title AS section, 
year.title AS year,
mark.id, mark.th, mark.pr
FROM mark 
LEFT JOIN student ON student.id = mark.std_id   
LEFT JOIN year ON year.id = student.year 
LEFT JOIN class ON class.id = student.class 
LEFT JOIN section ON section.id = student.section
WHERE mark.std_id =:id

Answer 4

尝试一下

SELECT
        student.id, student.name,
        GROUP_CONCAT(CONCAT(subject.title,year.title,class.title,mark.th)) as Marks 
        FROM student
        LEFT JOIN year ON year.id = student.year 
        LEFT JOIN class ON class.id = student.class 
        LEFT JOIN mark ON mark.std_id = student.id
        LEFT JOIN subject ON subject.id = mark.sub_id
        WHERE student.id=:id
        GROUP BY student.id

MySQL加入获得重复结果

4 个答案: