如何改善php和MySQL中的查詢以快速顯示

Question

我在下面有兩個表：候選表存儲候選信息，表候選對象存儲結果。 我想從兩個表中查詢並在網頁上顯示結果

CREATE TABLE candidate_subjects (
  id INT(10) PRIMARY KEY NOT NULL AUTO_INCREMENT,
  candidate_id INT(11),
  exam_type_id INT(10),
  subject_id INT(10),
  ca_score INT(11),
  exam_score INT(6),
  score_grade VARCHAR(10),
  date_created VARCHAR(10),
  date_modified TIMESTAMP
);

INSERT INTO `candidate_subjects` (`id`, `candidate_id`, `exam_type_id`, 
`subject_id`, `ca_score`, `exam_score`, `score_grade`, `date_created`, 
`date_modified`) VALUES
  (1, 2, 1, 32, 22, 61, A, '2017-02-01', '2017-08-28 13:10:33'),
  (2, 2, 1, 5, 21, 38, B, '2017-02-01', '2017-08-28 13:10:33'),
  (3, 2, 1, 14, 21, 51, A, '2017-02-01', '2017-08-28 13:10:33'),
  (4, 2, 1, 1, 19, 34, B, '2017-02-01', '2017-08-28 13:10:33'),
  (5, 2, 1, 2, 23, 39, B, '2017-02-01', '2017-08-28 13:10:33'),
  (6, 2, 1, 38, 20, 32, B, '2017-02-01', '2017-08-28 13:10:33'),
  (7, 2, 1, 53, 24, 47, A, '2017-02-01', '2017-08-28 13:10:33'),
  (8, 4, 1, 32, 19, 61, A, '2017-02-01', '2017-08-28 13:11:27'),
  (9, 4, 1, 5, 22, 41, B, '2017-02-01', '2017-08-28 13:11:27'),
  (10, 4, 1, 14, 20, 46, A, '2017-02-01', '2017-08-28 13:11:27'),
  (11, 4, 1, 1, 23, 37, B, '2017-02-01', '2017-08-28 13:11:27'),
  (12, 4, 1, 2, 21, 36, B, '2017-02-01', '2017-08-28 13:11:27'),
  (13, 4, 1, 38, 22, 34, B, '2017-02-01', '2017-08-28 13:11:27'),
  (14, 4, 1, 53, 24, 52, A, '2017-02-01', '2017-08-28 13:11:27'),
  (15, 5, 1, 32, 20, 62, A, '2017-02-01', '2017-08-28 13:11:44'),
  (16, 5, 1, 5, 22, 38, B, '2017-02-01', '2017-08-28 13:11:44');


CREATE TABLE candidates (
  id INT(11) PRIMARY KEY NOT NULL AUTO_INCREMENT,
  exam_no VARCHAR(15),
  surname VARCHAR(50),
  other_names VARCHAR(100),
  school_id INT(11),
  registration_completed INT(11),
  exam_scores_completed INT(5),
  remark VARCHAR(10)
);

INSERT INTO candidates (id, exam_no, surname, other_names, school_id,
registration_completed, exam_scores_completed, remark) VALUES
 (1, '1171052001', 'ABADO', 'MASENENGEN', 1052, 1, '1', 'RESIT'),
 (2, '1170938001', 'AGBA', 'NGUHER', 938, 1, '1', 'FAIL'), 
 (3, '1170071001', 'ABEE', 'SESUUR', 71, 1, '1', 'PASS'),
 (4, '1170938002', 'AHEN', 'REBECCA DOOSUUN', 938, 1, '1', 'PASS');

我有一個函數可以在候選人表中獲取候選人的學科成績。

    function getgradebycandsub($candidate_id, $sub){

        $s = "SELECT score_grade FROM `candidate_subjects` WHERE candidate_subjects.candidate_id='$candidate_id' AND candidate_subjects.subject_id='$sub'";

            $r = mysql_query($s);
            $c = mysql_fetch_array($r);
            return $c['score_grade'];
     }

我有以下循環：

      $s = "SELECT id, exam_no, surname, other_names, remark FROM candidates ORDER BY surname";
    $r = mysql_query($s);

echo "<tr><td align='center'>S/N</td><td align='center'>EXAM NO.</td><td align='center'>NAMES OF CANDIDATES</td><td align='center'>ENG</td><td align='center'>MATH</td><td align='center'>B.STD</td><td align='center'>C.ART</td><td align='center'>FREN</td><td align='center'>HAU</td><td align='center'>BST</td><td align='center'>ARAB</td><td align='center'>P.VOC</td><td align='center'>R.N.V</td><td align='center'>REMARK</td></tr>";
 while ($candidates = mysql_fetch_array($r)) {

        echo "<tr>";
        echo "<td height='30'>" . ++$sno . "</td>";
        echo "<td>" . $candidates['exam_no'] . "</td>";
        echo "<td>" . $candidates['surname'] . "&nbsp;&nbsp; " . $candidates['other_names'] . "</td>";
        echo "<td align='center'>".getgradebycandsub($candidates['id'], '1')."</td>";
        echo "<td align='center'>".getgradebycandsub($candidates['id'], '2')."</td>";
        echo "<td align='center'>".getgradebycandsub($candidates['id'], '5')."</td>";
        echo "<td align='center'>".getgradebycandsub($candidates['id'], '14')."</td>";
        echo "<td align='center'>".getgradebycandsub($candidates['id'], '22')."</td>";
        echo "<td align='center'>".getgradebycandsub($candidates['id'], '53')."</td>";
        echo "<td align='center'>".getgradebycandsub($candidates['id'], '32')."</td>";
        echo "<td align='center'>".getgradebycandsub($candidates['id'], '33')."</td>";
        echo "<td align='center'>".getgradebycandsub($candidates['id'], '38')."</td>";
        echo "<td align='center'>".getgradebycandsub($candidates['id'], '27')."</td>";
        echo "<td align='center'>".$candidates['remark']."</td>";
        echo "</tr>";
    }

我的挑戰是顯示5條記錄需要5個小時。 UPDATE
預期的輸出是S / No，考試編號，名稱，ENG，MATH，B.STD，C.ART，FREN，HAU，BST，ARAB，P.VOC，RNV和REMARK。 那是候選人的詳細信息，例如考試編號，姓名，科目的成績和備注

Answer 1

使用JOIN代替function調用將提高性能。 因為，在每個函數調用中，您都再次執行查詢，該查詢將進入數據庫並獲取結果，從而導致性能下降。

SELECT score_grade, id, exam_no, surname, other_names, remark 
FROM candidate_subjects cs
INNER JOIN  candidates  ON 
cs.candidate_id=c.id ORDER BY id, subject_id;

它將按學生ID和科目返回結果順序。