PHP脚本不适用于我的db [duplicate]

I've written following php script:

$sql = "SELECT * FROM `URLs` WHERE `durchsucht` = \'0\' LIMIT 0, 1 ";
$result = mysqli_query($db, $sql);

$row = mysqli_fetch_row($result);

$URL = $row['URL'];
echo $row['URL'];

unfortunately I get this error:

'mysqli_fetch_assoc() expects parameter 1 to be mysqli_result boolean given'

I've already got another table (within the same db) and there works this code... I appreciate every answer!

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Your result set may have zero records, so you can make use of $result->num_rows to check whether result set has data or not

if ($result->num_rows > 0)
{
     $row = mysqli_fetch_row($result);
     $URL = $row['URL'];
     echo $row['URL'];
}