php - 优化循环 select 语句

Question

所以我目前有一个包含调查问题的数据库，现在想要显示结果。 注意事项:每个问题可以有 2-6 个答案，具体取决于问题。

这些是我正在使用的表格和一些示例数据:

 Table: answers_only         Table: questions_only
╔════════════════╦════════╗ ╔═════════════════╦═══════════════════╗
║ answer_ID (PK) ║ answer ║ ║question_ID (PK) ║ question          ║
╠════════════════╬════════╣ ╠═════════════════╬═══════════════════╣
║    65114       ║ yes    ║ ║       123       ║ Are you happy?    ║
╚════════════════╩════════╝ ╚═════════════════╩═══════════════════╝

                    Table: questions
╔════════════════╦══════════════════╦════════════════╦════════════════╗
║ unique_ID (PK) ║ question_ID (FK) ║ answer_ID (FK) ║ person_ID (FK) ║
╠════════════════╬══════════════════╬════════════════╬════════════════╣
║              1 ║              123 ║          65114 ║           5521 ║
╚════════════════╩══════════════════╩════════════════╩════════════════╝

所以我有一个表questions，其中包含questions_only的ID(FK)，其中包含实际问题。我在这里列出了回答最多的 100 个问题:

$result = mysqli_query($con,"SELECT question, questions.question_ID AS question_ID 
FROM questions 
INNER JOIN questions_only ON questions_only.question_ID=questions.question_ID 
GROUP BY questions.question_ID 
ORDER BY COUNT(*) DESC limit 100");

接下来，我会仔细检查每个问题并收集每个答案的数量:

while($row = mysqli_fetch_array($result)) {

    $question_ID = $row['question_ID'];

    $result2 = mysqli_query($con,"SELECT answer, COUNT(*) AS 'count' 
    FROM questions 
    INNER JOIN answers_only ON answers_only.answer_ID=questions.answer_ID 
    WHERE questions.question_ID= '" . $question_ID . "' 
    GROUP BY answer ORDER BY COUNT(*) DESC"); 
}

目前第一行代码的执行时间约为8秒。第二部分(循环 100 个 select 语句)大约需要 350 秒。所以我正在寻找更好的方法来做到这一点，因为目前它在这种时候不可用。目前此代码在文档的 head 标记中运行。

Answer 1

当这样的事情占用大量时间时，也许你的服务器会超时。在这些情况下，解决问题的一种方法是使用每行输出调用数据库。也就是说，更改将数据分成不同部分的策略，以保持连接处于事件状态，并为用户等待的每一秒提供一些反馈。

一个看起来像这样的过程可能会这样:

// get all of the question ids that matter.
$result = mysqli_query($con,"SELECT questions.question_ID AS question_ID 
FROM questions DESC limit 100");  // or similar
// pack all of those into an array
$answerHolder = array();
while($row = mysqli_fetch_array($result)) {

    $question_ID = $row['question_ID'];
    $answerHolder[] = $questionID;
}
// iterate through that array to get the questions that match each id

foreach ($answerHolder as $item){
// use $item in a SQL call to get the question
// as each question is obtained, print it out to display or store it for later use
}

与此类似的过程模式的更改将有助于保持数据库连接处于事件状态，并可能提供足够及时的反馈来保持用户的兴趣。每当他们等待超过 10 秒时，您可能需要考虑向他们提供某种进度声明，让他们知道程序正在运行。

这种方法不会快得多，但它可能会让用户和系统致力于解决手头的问题。