PHP SQL，如何查询帖子中的评论数（对于博客帖子）？

Question

我目前正在使用自定义CSS创建自己的博客，该CSS是使用PHP从头开始构建的。 我对语言和SQL还是很陌生。 现在，我在从数据库查询的每条帖子上显示Comments(3)链接时遇到问题。 我有3个表格：用户，帖子和评论。

用户

id | username | password | name | email | privileges

帖子

postid | title | date | content | userid | visible | active 

评论

commentid | c_name | c_email | c_ website | c_date | c_content | approved | postid

这是我当前的查询，用于显示数据库中的帖子内容：

 $query = connect()->prepare(
    "SELECT * FROM posts JOIN users on posts.userid = users.id WHERE visible = 1 ORDER BY postid DESC");
$query->execute();

<div id="posts">
            <?php
               while($posts = $query->fetch(PDO::FETCH_ASSOC)) {
                $id = $posts['postid'];
                $title = $posts['title'];
                $date = $posts['date'];
                $content = $posts['content'];
                $name = $posts['name'];
            ?>
            <div id="entry" class="post-<?php echo $id; ?>">            
                <h1><?php echo "<a href='entry.php?id=".$id."'>" .$title. "</a>"; ?></h1>
                <div class="entry_content">
                    <?php echo $content; ?>
                    <p><span class="author"><?php echo $name; ?> on <?php echo $date;?></span></p>
                  //this is where I want to put the "Comments(3)"
                </div>
            </div>
            <?php } ?>
        </div>

我尝试执行以下查询，以通过其帖子ID INSILDE while循环找到它来检索评论数。

 <?php 
       $query = connect()->prepare("SELECT COUNT(postid) as commmentno FROM comments WHERE postid = :postid");
       $query->execute(array(':postid' => $id)); 
       $commentnos = $query->fetch();

       echo $commentnos['commentno'];
  ?>

但是结果结果是，我只显示了一条带有正确数量的评论的帖子...如何在一个查询中获得这些结果？

Answer 1

单个查询的工作方式如下：

SELECT
    posts.id, posts.title, posts.date, posts.content, posts.name,
    (SELECT COUNT(postid) FROM comments WHERE postid = posts.id) as commmentno
FROM posts
JOIN users on posts.userid = users.id
WHERE visible = 1
ORDER BY postid DESC

然后，根本不需要内部查询，因为主要查询将注释计数作为字段返回。

Answer 2

我相信您已经使用相同的变量名$query来获取帖子数据和评论号。 当您使用相同的变量名$ query $query = connect()->prepare("SELECT COUNT(postid) as commmentno FROM comments WHERE postid = :postid"); 它会覆盖先前的查询结果。 这样一来，您只有一个显示正确评论数的帖子。 尝试将代码更改为

<?php 
       $commentquery = connect()->prepare("SELECT COUNT(postid) as commmentno FROM comments WHERE postid = :postid");
       $commentquery->execute(array(':postid' => $id)); 
       $commentnos = $commentquery->fetch();

       echo $commentnos['commentno'];
  ?>

Answer 3

您可以尝试以下方法：

$query = connect()->prepare(
"SELECT * FROM posts JOIN users on posts.userid = users.id WHERE visible = 1 ORDER BY postid DESC");
$query->execute();

<div id="posts">
        <?php
           while($posts = $query->fetch(PDO::FETCH_ASSOC)) {
            $id = $posts['postid'];
            $title = $posts['title'];
            $date = $posts['date'];
            $content = $posts['content'];
            $name = $posts['name'];
        ?>
        <div id="entry" class="post-<?php echo $id; ?>">            
            <h1><?php echo "<a href='entry.php?id=".$id."'>" .$title. "</a>"; ?></h1>
            <div class="entry_content">
                <?php echo $content; ?>
                <p><span class="author"><?php echo $name; ?> on <?php echo $date;?></span></p>
              //this is where I want to put the "Comments(3)"
             $cquery = connect()->prepare("SELECT COUNT(commentid) as commentno FROM comments WHERE postid='".$id."'");
             $cquery->execute();
             $result = $cquery->fetch(PDO::FETCH_ASSOC);
             echo $result['commentno'];
            </div>
        </div>
        <?php } ?>
    </div>