我试图从特定的表、行和列中提取一个数字，但似乎无法正确提取。
该表为tblproducts。该列为qty。我需要选择其中id是13。
这是我正在使用的代码，但它没有返回任何内容：
<?php
$con=mysqli_connect("localhost","blank","blank","blank");
// Check connection
if (mysqli_connect_errno())
{
echo "Failed to connect to MySQL: " . mysqli_connect_error();
}
$result = mysqli_query($con,"SELECT qty FROM tblproducts");
while($row = mysqli_fetch_array($result))
{
echo $row['13'];
}
mysqli_close($con);
?>
如有任何帮助，将不胜感激
像一样在查询中完成所有操作
SELECT qty FROM tblproducts where id =13
无需环路
$result = mysqli_query($con,"SELECT qty FROM tblproducts where id =13");
$row = mysqli_fetch_assoc($result);
echo $row['qty'];
您的sql语法有点错误，请参阅我的更正。你的row['13']回声看起来也很可疑。您可以使用print_r()打印数组，以查找需要使用的密钥。可能是$row['qty']。
<?php
$con=mysqli_connect("localhost","blank","blank","blank");
// Check connection
if (mysqli_connect_errno())
{
echo "Failed to connect to MySQL: " . mysqli_connect_error();
}
$result = mysqli_query($con,"SELECT qty FROM tblproducts where id = 13");
while($row = mysqli_fetch_array($result))
{
print_r($row); // You can use print_r to have a look at your full array. The index '13' might not be what you where looking for.
}
mysqli_close($con);
?>