Question

我可以用几个foreach语句解决此问题，但是当每个班级有26名学生并且某些科目最多包含13个“ radnummer”时，要永久加载页面。请参阅下面的示例。

这是我希望输出的内容（行和列）：

问题：需要永久加载。

问题：我如何加快速度并提高效率？

表1，我选择了班级中的所有学生（选择1）：

SELECT `intressenter_alla`.id, `intressenter_alla`.fornamn, `intressenter_alla`.efternamn
FROM `intressenter_alla` 
INNER JOIN `klass_elev` 
ON `intressenter_alla`.id = `klass_elev`.id
WHERE (`klass_elev`.klass = :klassen)
ORDER BY `intressenter_alla`.efternamn, `intressenter_alla`.fornamn ASC

PRINT_R给出：

Array ( 

      [0] => Array ( 
      [id] => 1226 
      [0] => 1226 
      [lid] => 0 
      [1] => 0 
      [fornamn] => Peter
      [2] => Peter 
      [efternamn] => Strobe 
      [3] => Strobe 
      [personnr] => 070920-8690 
      [4] => 070920-8690 
      [mejl] => peter.strobe@mail.com  
      [5] => peter.strobe@mail.com  
      [6] => 1226 
      [klass] => 6B 
      [7] => 6B
)

      [1] => Array ( 
      [id] => 1227 
      [0] => 1227 
      [lid] => 0 
      [1] => 0 
      [fornamn] => Victor 
      [2] => Victor 
      [efternamn] =>Gand 
      [3] => Gand 
      [personnr] => 070518-8995 
      [4] => 070518-8995
      [mejl] => victor.gand@mail.com 
      [5] => victor.gand@mail.com
      [6] => 1227 
      [klass] => 6B 
      [7] => 6B
)
)

表2中，我为每个学生选择了相应的数据。这里有个问题。在此示例中，每个学生应针对此特定科目使用五行“ radnummer”（如下所示）。仅显示最后一个。应该在每行上显示一个特定的值“ kunsk_klick”。请参见下面的示例（SELECT 2）：

SELECT * 
FROM `iup_kunskapskrav_klick` 
WHERE elev_id = ? AND radnummer = ? AND amne_id = ? AND arskurs = ?
ORDER BY radnummer, datum DESC

PRINT_R给出：

Array ( 
   [kunsk_id] => 138557
   [0] => 138557 
   [amne_id] => 1 
   [1] => 1 
   [radnummer] => 5 
   [2] => 5 
   [elev_id] => 1226 
   [3] => 1226 
   [arskurs] => 5 
   [4] => 5 
   [lid] => 1 
   [5] => 1 
   [kunsk_klick] => E 
   [6] => E 
   [datum] => 2018-05-29 
   [7] => 2018-05-29 
) 

Array ( 

   [kunsk_id] => 138561 
   [0] => 138561 
   [amne_id] => 1 
   [1] => 1 
   [radnummer] => 5 
   [2] => 5 
   [elev_id] => 1227 
   [3] => 1227 
   [arskurs] => 5 
   [4] => 5 
   [lid] => 1 
   [5] => 1 
   [kunsk_klick] => E 
   [6] => E 
   [datum] => 2018-05-29 
   [7] => 2018-05-29 
)

编辑1：表的结构。

表intressenter_alla

CREATE TABLE `intressenter_alla` (
  `id` int(4) NOT NULL,
  `lid` int(3) NOT NULL,
  `fornamn` varchar(255) NOT NULL,
  `efternamn` varchar(255) NOT NULL,
  `personnr` varchar(12) NOT NULL,
  `mejl` varchar(255) NOT NULL
) ENGINE=InnoDB DEFAULT CHARSET=latin1;

表iup_kunskapskrav_klick

CREATE TABLE `iup_kunskapskrav_klick` (
  `kunsk_id` int(11) UNSIGNED NOT NULL,
  `amne_id` int(3) NOT NULL,
  `radnummer` int(10) NOT NULL,
  `elev_id` int(3) NOT NULL,
  `arskurs` int(2) NOT NULL,
  `lid` int(3) NOT NULL,
  `kunsk_klick` varchar(3) COLLATE utf8_swedish_ci NOT NULL,
  `datum` date NOT NULL
) ENGINE=MyISAM DEFAULT CHARSET=utf8 COLLATE=utf8_swedish_ci;

表klass_elev

CREATE TABLE `klass_elev` (
  `id` int(5) NOT NULL,
  `klass` varchar(2) NOT NULL
) ENGINE=InnoDB DEFAULT CHARSET=latin1 COMMENT='Elevid och klass.';

编辑2：示例代码（我知道，PHP和HTML混合不好，缩进也很差..）。

<?php

// All students (See SELECT number 1)
$hamta_hela_klassen = $anvandare->klasslista($_GET['klass']);

// Count how many radnummer there is in the subject
$count = 0;
$count = $abb->rakna_kunskapskrav($_GET['amne_id'], $arskursens);

echo "<table>";
echo "<thead>";
echo "<tr><th>Nr.</th><th>Picture</th><th>Name</th>";
if ($count<=1){
    echo "<th scope='row' style='vertical-align:middle;text-align:center'>Kunskapskrav</th>";
} else {
    for($i=1;$i<=$count;$i++)
    {
        // This outputs R1 - R2 and so on in the header of the columns (see the picture above)
        echo "<th width='1%' scope='row' style='vertical-align:middle;text-align:center'>R".$i."</th>";
    }
}

echo "<th>Date</th><th>Button</th>";

$raknare = 0;

// Loop out each student. Not the most effective way...                                                               
foreach ($hamta_hela_klassen as $klassuppgifter){
    $raknare++;

    // Profile picture
    $profilbild = '/home/jo/public_html/no/students/profilbilder/'.$klassuppgifter['id'].'.jpg';

    echo "<td>";
    echo AKTIV_URL."students/profilbilder/".$klassuppgifter['id'].".jpg";
    echo "</td>";

    // NAME
    echo "<td>";
    echo $klassuppgifter['fornamn']." ".$klassuppgifter['efternamn'];
    echo "</td>";

    if ($count<=1){
        echo "<td>Empty.</td>";
    } else {for($i=1;$i<=$count;$i++)
    {

        // Fetching each corresponding RADNUMMER for each student (see SELECT 2 above)                                      

        $iup_info_k1 = $iup->hamta_ett_kunskapskrav_klick_klass($klassuppgifter['id'], $i,$_GET['amne_id'], $arskursen);

        if (empty($iup_info_k1) && ($arskursen == '5' || $arskursen =='6' || $arskursen =='8' || $arskursen =='9')){
            $arskursen_lager = $arskursen -1;
            $iup_info = $iup->hamta_ett_kunskapskrav_klick_klass($klassuppgifter['id'], $i,$_GET['amne_id'], $arskursen_lager);
        } else {
            $iup_info = $iup_info_k1;
        }

        //Special for students in 4 - 5
        if ($arskursen=='4' || $arskursen=='5') {
            if ($iup_info['kunsk_klick'] == "G"){$betyget = 'P';}
            if ($iup_info['kunsk_klick'] == "F"){$betyget = 'O';}
            elseif ($iup_info['kunsk_klick'] == "E"){$betyget = '1';}
            elseif ($iup_info['kunsk_klick'] == "C"){$betyget = '2';}
            elseif ($iup_info['kunsk_klick'] == "A"){$betyget = '3';}
            elseif (empty($iup_info['kunsk_klick'])) {$betyget = "P"; }
        }

        //Special for students in 6 - 9
        if ($arskursen=='6' || $arskursen=='7' || $arskursen=='8' || $arskursen=='9') {
            if ($iup_info['kunsk_klick'] == "G"){$betyget = 'P';}
            elseif (empty($iup_info['kunsk_klick'])) {$betyget = "P"; }
            else { $betyget = $iup_info['kunsk_klick']; }
        }
        echo "<td>".$betyget."</td>";
    }
    }

    // DATE
    echo "<td>";
    echo $iup_info['datum'];
    echo "</td>";

    // Edit button
    echo "<td>";
    echo "EDIT";
    echo "</td>";


}

echo "</tr>";

echo "</tbody>";
echo "</table>";

?>

编辑3：

要仅输出命名列数据，而不是输出数字索引数据（我更改了fetch语句）：

$ pdo-> fetchAll（PDO :: FETCH_ASSOC）;

现在看起来像这样：

    Array ( 
       [kunsk_id] => 138561 
       [amne_id] => 1 
       [radnummer] => 5 
       [elev_id] => 1227 
       [arskurs] => 5 
       [lid] => 1 
       [kunsk_klick] => E 
       [datum] => 2018-05-29 
    )

Answer 1

从Per76的答复来看，此评论似乎是一种有效的解决方案：

您的MySQL Schema表似乎都没有索引。

因此...将索引添加到您的SQL表中。理想情况下，您应该在任何WHERE子句，任何JOIN子句或任何ORDER BY中引用的所有列都建立索引。索引是MySQL速度的关键。

Maximizing Query Performance through Column Indexing in MySQL

How do MySQL indexes work?

How do I add indices to MySQL tables?

注意：：此处列出的建议是微优化，只会对页面加载时间和/或效率产生最小的影响。这些只是调整，与如上所述在MySQL中实现适当的列索引所获得的改进相比，它们的改进将显得苍白。

使用switch PHP语句而不是重复的elseif。

    if ($iup_info['kunsk_klick'] == "F"){$betyget = 'O';}
    elseif ($iup_info['kunsk_klick'] == "E"){$betyget = '1';}
    elseif ($iup_info['kunsk_klick'] == "C"){$betyget = '2';}
    elseif ($iup_info['kunsk_klick'] == "A"){$betyget = '3';}
    elseif (empty($iup_info['kunsk_klick'])) {$betyget = "P"; }

成为

    switch($iup_info['kunsk_klick']) {
         case "F":
             $betyget = 'O';
             break;
         case "E":
             $betyget = '1';
             break;
         case "C":
             $betyget = '2';
             break;
         case "A":
             $betyget = '3';
             break;
         case "":
             $betyget = 'P';
             break;
    }

对列定义使用正确的MySQL Integer type。您只有3、4或5列长度的许多INT列都可以是UNSIGNED SMALLINT。
统一您的MySQL列数据类型，以便将INT(4)和INT(4)子句中的JOIN列与其他WHERE列进行比较。
使用utf8mb4字符集和排序规则，而不要使用笨拙的3字节UTF-8（huh? Wtf?）
if语句中的类型转换效率：(int)$arskursen===6比$arskursen=='6'更快，更高效（通过微小的标记）

修复您的PHP，使其仅输出 named 列数据，而不是数字索引数据（您正在使用的数据量是PHP）。示例：

Array ( 
   [kunsk_id] => 138561 
   [amne_id] => 1 
   [radnummer] => 5 
   [elev_id] => 1227 
   [arskurs] => 5 
   [lid] => 1 
   [kunsk_klick] => E 
   [datum] => 2018-05-29 
)

有效的PHP数组并选择

1 个答案: