mysqli_fetch_assoc() 期望参数 1 是 mysqli_result，给定布

mysqli_fetch_assoc() expects parameter 1 to be mysqli_result, boolean given(mysqli_fetch_assoc() 期望参数 1 是 mysqli_result，给定布尔值)

问题描述

我对 PHP 和 MySQL 还是很陌生，我就是想不通.我在论坛上到处搜索，但没有找到我能理解的答案.我最初使用 mysql_fetch_assoc() 但我只能搜索数字并且在搜索字母时也收到错误.我希望我在这里走在正确的轨道上.在此先感谢您的帮助！

I am pretty new to PHP and MySQL and I just can't figure this one out. I have searched all around the forum but haven't found an answer I can make sense of. I originally was using mysql_fetch_assoc() but I could only search numbers and I received errors when searching for letters as well. I hope I am on the right track here. Thank you in advance for all your help!

$con = mysqli_connect($hostname,$username,$password) or die ("<script language='javascript'>alert('Unable to connect to database')</script>");
mysqli_select_db($con, $dbname);

if (isset($_GET['part'])){
    $partid = $_GET['part'];
    $sql = 'SELECT * 
        FROM $usertable 
        WHERE PartNumber = $partid';

    $result = mysqli_query($con, $sql);
    $row = mysqli_fetch_assoc($result);

    $partnumber = $partid;
    $nsn = $row["NSN"];
    $description = $row["Description"];
    $quantity = $row["Quantity"];
    $condition = $row["Conditio"];
}

推荐答案

当您的结果不是结果(而是假")时会发生这种情况.你应该改变这一行

This happens when your result is not a result (but a "false" instead). You should change this line

$sql = 'SELECT * FROM $usertable WHERE PartNumber = $partid';

为此:

$sql = "SELECT * FROM $usertable WHERE PartNumber = $partid";

因为 " 可以解释 $variables 而 ' 不能.

because the " can interprete $variables while ' cannot.

适用于整数(数字)，对于字符串，您需要将 $variable 放在单引号中，例如

Works fine with integers (numbers), for strings you need to put the $variable in single quotes, like

$sql = "SELECT * FROM $usertable WHERE PartNumber = '$partid' ";

如果你想/必须使用单引号，那么php不能解释变量，你必须这样做:

If you want / have to work with single quotes, then php CAN NOT interprete the variables, you will have to do it like this:

 $sql = 'SELECT * FROM '.$usertable.' WHERE string_column = "'.$string.'" AND integer_column = '.$number.';

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