我一直在思考这个问题，我想我会问一些了解 MySQL 甚至 PHP 的人。假设您有一个获取文章动态信息的查询。您还有几个与文章相关联的表，例如评论和类别。假设您希望在文章结果页面上获取评论数量和文章所属类别等信息。哪种方法加载速度更快？
一个大型查询:
$query = "
SELECT
a.article_id, a.title, a.description, a.category_id
com.comment_id, com.article_id, COUNT(com.article_id) AS num_comments
cat.category_id, cat.title AS cat_titleca
FROM articles AS A
LEFT JOIN categories AS cat ON (a.category_id = cat.category_id)
LEFT JOIN comments AS com ON (a.article_id = com.comment_id)
GROUP BY a.article_id
ORDER BY a.article_id DESC
LIMIT 10";
if($query = mysql_query($query)){
if(mysql_num_rows($query) > 0){
while($article=mysql_fetch_assoc($query)){
echo $article['title'].' has '.$article['num_comments'].' comments and is in the category '.$article['cat_title'].'.';
}
}
}
或者使用几个较小的查询:
<?php
$query_articles = "
SELECT
article_id, title, description, category_id
FROM articles
ORDER BY article_id DESC
LIMIT 10";
if($query_articles = mysql_query($query_articles)){
if(mysql_num_rows($query_articles) > 0){
while($article=mysql_fetch_assoc($query_articles)){
$query_comments = "
SELECT
comment_id, article_id
FROM comments
WHERE article_id = ".$article['article_id']."
ORDER BY comment_id";
if($query_comments = mysql_query($query_comments)){
$num_comments = mysql_num_rows($query_comments);
}
$query_cat = "
SELECT
category_id, title
FROM categories
WHERE category_id = ".$article['category_id']."
LIMIT 1";
if($query_cat = mysql_query($query_cat)){
if(mysql_num_rows($query_cat) > 0){
$cat = mysql_fetch_assoc($query_cat);
}
}
echo $article['title'].' has '.$num_comments.' and is in the category '.$cat['title'].'.';
}
}
}
最佳答案
单个查询当然更快，你为什么不做基准测试
$time = microtime(true);
//code here
$elapsed = microtime(true) - $time;
echo 'Elapsed time = '.$elapsed;
关于php - 使用一个大查询还是多个小查询更快？，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/26476783/