获取一组获取的字段值的计数 - MySQL / PHP

Question

我从 MySQL 数据库返回了一些数据，该数据库输出特定用户的 post 详细信息。

我想输出图像数量的计数（在下面用 $db_image_filename 值表示）。

如何计算列中字段值的数量？我以为我可以使用 PHP 的 count() 功能，但这不起作用？

有没有办法在 PHP 中执行此操作而无需运行对数据库进行另一个查询（因为此数据已经从数据库中获取，我只需要它的计数值）？然后，该值将在下面示例底部的 <p> 标记中回显。

<?php

    $stmt = $connection->prepare("SELECT * FROM imageposts WHERE username = :username");
    $stmt->bindParam(':username', $username);
    $stmt->execute();   

    while ($row = $stmt->fetch()) {

    $db_image_id = htmlspecialchars($row['image_id']);
    $db_image_title = htmlspecialchars($row['image_title']);
    $db_image_tags = htmlspecialchars($row['image_tags']);
    $db_image_filename = htmlspecialchars($row['filename']);

?>
<figure>

   <!-- html is outputted here including values using the PHP variables above -->

</figure>

<p>Number of images: <?php // echo the count value of $db_image_filename ?></p>

<?php } ?>

Answer 1

在 while 循环之前和循环内部定义一个变量 $count_images = 0，每次出现 $row['filename'] 而不是 NULL 时，将变量增加 +1 或空字符串。

在 while 循环之后你可以 echo $count_images:

<?php
    $stmt = $connection->prepare("SELECT * FROM imageposts WHERE username = :username");
    $stmt->bindParam(':username', $username);
    $stmt->execute();   

     $count_images = 0;  // AT THE BEGINNING THERE ARE 0 IMAGES

    while ($row = $stmt->fetch()) {   // LOOP START

    $db_image_id = htmlspecialchars($row['image_id']);
    $db_image_title = htmlspecialchars($row['image_title']);
    $db_image_tags = htmlspecialchars($row['image_tags']);
    $db_image_filename = htmlspecialchars($row['filename']);

    if ($db_image_filename != NULL  && $db_image_filename != '') {
         $count_images++;  // IF IMAGE FOUND, INCREASE BY +1
    }

?>
<figure>

   <!-- html is outputted here including values using the PHP variables above -->

</figure>
<?php } // END OF WHILE LOOP ?>

<p>Number of images: <?php echo $count_images; ?></p>

获取一组获取的字段值的计数 - MySQL / PHP

Get Count For A Set Of Fetched Field Values - MySQL / PHP

php

mysql

count

fetch