Question

$value1 = $_POST['user'];
$dbc =mysqli_query($conn,"SELECT * FROM userdetails where (usernamename = '$value1') ");
if (mysqli_num_rows($dbc)>0)
    echo "success";
else
    echo "duplicate entry";

这是我的代码。但它返回

警告：mysqli_num_rows（）期望参数1为mysqli_result，第17行/home/u415962859/public_html/signupexe.php中给出的布尔值重复条目

即使不是，也会显示重复的条目。请帮忙

Answer 1

检查您的查询是否失败。

$value1 = $_POST['user'];
$dbc =mysqli_query($conn,"SELECT * FROM userdetails where (usernamename = '$value1') ");
if (is_resource($dbc) and mysqli_num_rows($dbc)>0)
// OR
// if ($dbc !== false and mysqli_num_rows($dbc) > 0)
// I used !== instead of != as I consider it to be a good practice when checking
// values that are expected to have multiple data types, not only boolean.
    echo "success";
else
    echo "duplicate entry";

Answer 2

试试这个：

$value1 = $_POST['user'];

$dbc =mysqli_query($conn,"SELECT * FROM userdetails where username = '$value1' ");

if (mysqli_num_rows($dbc)>0){

echo "success";

  } else {

echo "duplicate entry";

}

Answer 3

如果查询失败，mysqli_query将返回false而不是结果。这就是出现此警告的原因。

由于mysqli_num_rows失败，它也返回false并执行else-block。

在将错误提供给其他命令之前，检查mysqli_query的结果是否有错误：

$value1 = $_POST['user'];
$dbc =mysqli_query($conn,"SELECT * FROM userdetails where (usernamename = '$value1') ");

// Check result from mysqli_query
if(!$dbc) die('mysqli_query error: ' . mysqli_error($conn));

if (mysqli_num_rows($dbc)>0)
    echo "success";
else
    echo "duplicate entry";

Answer 4

如果a=raw_input("Enter the name of the School") l=list() for i in a: l.append(i) print l z=0 empty=" " for i in l: print for j in range(0,z+1): kl=l(j) print empty+j, z+=1是布尔值，则表示查询本身或连接中存在错误。尝试

Traceback (most recent call last):
  File "C:/Python27/triaangle.py", line 12, in <module>
    kl=l(j)
TypeError: 'list' object is not callable

找到原因。

Answer 5

试试这个：

Yii::$app->request->bodyParams;

Answer 6

您的代码在查询执行失败时使用mysqli_error获取更具体的错误看起来很好：

$value1 = $_POST['user']; 

$dbc = mysqli_query($conn,"SELECT * FROM userdetails 
WHERE usernamename = '$value1' "); 

if(!$dbc) {
die('DATABASE ERRORS: ' . mysqli_error($conn)); 
}

if (mysqli_num_rows($dbc)>0) {
     echo "success"; 
}
else {
     echo "duplicate entry";
}

旁注：

正如我在评论中提到的，必须检查您的列名称我100％确定其错字错误，您的列名称应为username而不是usernamename。

arning：mysqli_num_rows（）期望参数1为mysqli_result，给定布尔值

6 个答案: