PHP SQL，如何查詢帖子中的評論數（對於博客帖子）？

Question

我目前正在使用自定義CSS創建自己的博客，該CSS是使用PHP從頭開始構建的。 我對語言和SQL還是很陌生。 現在，我在從數據庫查詢的每條帖子上顯示Comments(3)鏈接時遇到問題。 我有3個表格：用戶，帖子和評論。

用戶

id | username | password | name | email | privileges

帖子

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

評論

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

這是我當前的查詢，用於顯示數據庫中的帖子內容：

 $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>

我嘗試執行以下查詢，以通過其帖子ID INSILDE while循環找到它來檢索評論數。

 <?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'];
  ?>

但是結果結果是，我只顯示了一條帶有正確數量的評論的帖子...如何在一個查詢中獲得這些結果？

Answer 1

單個查詢的工作方式如下：

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，根本不需要內部查詢，因為主要查詢將注釋計數作為字段返回。

Answer 2

我相信您已經使用相同的變量名$query來獲取帖子數據和評論號。 當您使用相同的變量名$ query $query = connect()->prepare("SELECT COUNT(postid) as commmentno FROM comments WHERE postid = :postid"); 它會覆蓋先前的查詢結果。 這樣一來，您只有一個顯示正確評論數的帖子。 嘗試將代碼更改為

<?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

您可以嘗試以下方法：

$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>