Question

这是我的代码。实际上它运行没有错误，但它总是进入第一个条件，即使mysql中的值大于0，例如是10。

<?php
session_start();
$loginuser = $_SESSION['result'];
$con=mysqli_connect("localhost","root","","leavecalendar");
// Check connection
if (mysqli_connect_errno())
 {
 echo "Failed to connect to MySQL: " . mysqli_connect_error();
 }
$sql="SELECT leavecount from employee WHERE username = $loginuser[username]";
$resource = mysql_query($sql);
if ($resource == 0) {
echo "ajsdjsdasjd";   <----always enters here
 }
else
{
header("insert.php");
} 

mysqli_close($con);
?>

Answer 1

首先，你正在混合api。不要混用mysqli_*和mysql_*。坚持使用mysqli_*。

$con = mysqli_connect("localhost","root","","leavecalendar"); // mysqli
$resource = mysql_query($sql); // mysql

其次，由于您现在使用mysqli_*，只需使用预准备语句。

$sql="SELECT leavecount from employee WHERE username = $loginuser[username]";

第三，不要将结果集与零进行比较，而是检查结果返回的行数。

$resource = mysqli_query($con, $sql);
if ($resource == 0) {

考虑这个例子：

session_start();
if(isset($_SESSION['result'])) {
    $mysqli = mysqli_connect("localhost","root","","leavecalendar");
    $loginuser = $_SESSION['result'];
    $stmt = $mysqli->prepare("SELECT leavecount from employee WHERE username = ?");
    $stmt->bind_param("s", $loginuser);
    $stmt->execute();

    if($stmt->num_rows > 0) {
        // if it has results
        header("Location: insert.php");
    } else {
        // if it has NO results
    }
}

Answer 2

的问题

1）您无法使用

mysql_query($query)

对于mysqli

2）

"SELECT leavecount from employee WHERE username = $loginuser[username]"

用户名应为单引号或双引号。例如："SELECT leavecount from employee WHERE username = 'dineshrawat'";

<强>解决方案

<?php session_start(); $loginuser = $_SESSION['result']; $con=mysqli_connect("localhost","root","","leavecalendar"); // Check connection if (mysqli_connect_errno()) { echo "Failed to connect to MySQL: " . mysqli_connect_error(); } $sql="SELECT leavecount from employee WHERE username = $loginuser[username]"; $resource = mysqli_query($con, $sql); if ($resource == 0) { // If there is no record in result set echo "No record found"; } else { header("insert.php"); } mysqli_close($con); ?>

mysql检查值是否大于0

2 个答案: