PHP&MySQL检查表是否为空 [英] PHP & MySql check if table is empty

问题描述

我有点菜鸟，我很难受...

I'm a bit of a noob- and I'm having a hard time...

我需要一些代码来搜索数据库表以查找与$ id变量匹配的行.该表"description"中有一个字段需要我抓取.如果为空，我需要显示一条消息，如果不是另一条消息.这是我的代码(我知道我需要添加mysqli转义字符串，只需从内存中快速完成此操作即可):

I need a bit of of code that searches a db table to find the row that matches the $id variable. There's a field in that table 'description' that I need to grab. If it's null, I need to show one message, if not another. Here's the code I have (I know I need to add the mysqli escape string, just doing this real quick from memory):

$query = "SELECT description FROM posts WHERE id = $id";
$result = mysqli_query($dbc, $query);

$row = mysqli_fetch_array($result, MYSQLI_ASSOC) ;

if(!$row){
echo "<p>'No description'</p>";
} else {
echo '<p>' . $row['description'] . '</p>';
}

推荐答案

mysqli_fetch_array 将获取一行，无论该行中的列是否为空.您要检查是否设置了 $ row ['description'] ，而不是是否设置了 $ row :

mysqli_fetch_array will fetch a row regardless of if the columns in that row are null. You want to be checking if $row['description'] is set instead of if $row is set:

$query = "SELECT description FROM posts WHERE id = $id";
$result = mysqli_query($dbc, $query);

$row = mysqli_fetch_array($result, MYSQLI_ASSOC);

if(isset($row['description'])) {
    echo "<p>No description</p>";
} else {
    echo '<p>' . $row['description'] . '</p>';
}

或者，您也可以不从描述为NULL的数据库中获取行:

$query = "SELECT description FROM posts WHERE id = $id AND description IS NOT NULL LIMIT 1";
$result = mysqli_query($dbc, $query);

$row = mysqli_fetch_array($result, MYSQLI_ASSOC);

if(! $row) {
    echo "<p>No description</p>";
} else {
    echo '<p>' . $row['description'] . '</p>';
}

现在，您将检查是否可以抓行.

Now you'd check to see if you were able to grab a row or not.

这篇关于PHP&MySQL检查表是否为空的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！