MySQL：查询另一个查询结果并返回两个结果？

Question

I am using following 'php' and 'MySQL' code to list most recent topics from my database and to list related titles below each of those titles...

// First Query 
$query= mysql_query("SELECT * FROM my_table  ORDER BY id DESC limit 0,20");  
$result = mysql_query($query) 

while($row = mysql_fetch_array($result)){
echo "Main Topic: ".$row['title'];
$main_title = $row['title'];
    echo "Related to this Topic:";

   // Second Query 
    $related_query= mysql_query("
    SELECT * MATCH (title)
    AGAINST('$main_title'IN NATURAL LANGUAGE MODE)AS 
    score FROM my_table  MATCH(title)  AGAINST('$main_title'IN NATURAL LANGUAGE MODE)
    HAVING score > 10  ORDER BY score DESC
    ");  
    $related_result = mysql_query($related_query) 

            while($related_row = mysql_fetch_array($related_result)){
            echo  "<br>". $related_row['title'];
    }


}

This works fine. But the problem is that it uses a MySQL queries within a loop. (second query runs 20 times) I've read it is not a good programming practice because it uses server resources heavily.

So, is there a way to do this with just one query or two queries without having to run a query within a loop?

Thank you

Answer 1

First off, STOP USING mysql_*() functions. They have been deprecated for years.

Second, once you start using a reasonable database interface like PDO or even just mysqli, you can do prepared queries. The query can be prepared outside the loop, which will save resources and reduce the time taken.

Third, it's possible this could be done with one query, but would need DB structure posted to be certain.

EDIT: here's some untested PDO code:

<?php
try {
    $db = new PDO("mysql:host=localhost;dbname=my_database", "user", "pass");
} catch(PDOException $e) {
    echo $e->getMessage();
    exit;
}

$result = $db->query("SELECT * FROM my_table ORDER BY id DESC LIMIT 20");
$result->setFetchMode(PDO::FETCH_ASSOC);

$stmt = $db->prepare("SELECT * MATCH (title) AGAINST (? IN NATURAL LANGUAGE MODE) AS score FROM my_table MATCH (title) AGAINST (? IN NATURAL LANGUAGE MODE) HAVING score > 10  ORDER BY score DESC");

while ($row = $result->fetch()) {
    echo "Main Topic: $row[title]";
    $params = array($row["title"], $row["title"]);
    $result2 = $stmt->execute($params);
    $result2->setFetchMode(PDO::FETCH_ASSOC);
    while ($row2 = $result2->fetch()) {
        echo  "<br>$row2[title]";
    }
}