mysqli_fetch_assoc()期望参数1为mysqli_result，给定布尔值 [英] mysqli_fetch_assoc() expects parameter 1 to be mysqli_result, boolean given

问题描述

我对PHP和MySQL还是很陌生，我只是想不通.我搜索了整个论坛，但没有找到我能理解的答案.我最初使用的是mysql_fetch_assoc()，但我只能搜索数字，并且在搜索字母时也收到错误.我希望我在正确的轨道上.预先感谢您的所有帮助！

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"false")时，就会发生这种情况. 您应该更改此行

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';

对此:

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

因为可以解释$变量，而'不能.

because the " can interprete $variables while ' cannot.

可以很好地使用整数(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' ";

如果要/必须使用单引号，则php无法解释变量，则必须这样做:

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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