如果数据库中已经存在值

Question

首先，如果我选择“书包和汤”并单击“ 保存”按钮，则值将保存在数据库中，并重定向到 saveoutofstock.php < / strong>页面。很好....

第二次，如果我选择相同的选项-“ schoolbag＆Soup”，则它不会保存在数据库中[因为我在ALTER TABLE outofstock ADD UNIQUE account_prod (name(90), type(90));之前执行了此操作，但仍然重定向到saveoutofstock.php页面。但我不想重定向，而是要显示错误消息为名称并且类型已经存在

表格

<form name="adduserforms" id="adduserforms" action="saveoutofstock.php" >
<select name="names" id="names" onChange="changecat(this.value);">
        <option value="A">>A</option>
        <option value="B">>B</option>
</select>

<select name="department" id="department" class="username">
<option value="" disabled selected>Select</option>
</select>

<input type="button" id="assign" value="Save" onclick="assignusers();"/>    

saveoutofstock.php

<?php
$_SESSION['login_user'];

if(isset($_POST['edituser']) && $_POST['edituser']=="editUsers")
{
    if($_SESSION['login_user']=='admin')
    {
        $sql = "UPDATE outofstock set name='".$name."',type='".$type."' WHERE id=".$_POST['userId'];
    }   

    $redirectUrl="outofstocklist.php";
}

else if
{
$sql = "SELECT * FROM outofstock WHERE names = '".$name."' AND department ='".$type."' ";
    echo "name and type already exists";
}
 else
{

$sql = "INSERT INTO outofstock (name,type) VALUES ('".$name."','".$type."')";
$redirectUrl="outofstocklist.php";
}

$result = $db_handle->executeUpdate($sql);

?>

Answer 1

由于您在(name, type)上具有唯一索引，因此在尝试执行INSERT时会出错。您应该检查该错误。

$result = $db_handle->executeUpdate($sql);
if (!$result && mysqli_errno($db_handle) == 1022) {
    echo "name and type already exist";
}

1022是重复密钥的MySQL错误代码。

摆脱此代码块：

else if
{
$sql = "SELECT * FROM outofstock WHERE names = '".$name."' AND department ='".$type."' ";
    echo "name and type already exists";
}

语法错误，因为if之后没有任何条件。它也没有做任何有用的事情，因为它回显了在尝试执行获取错误的INSERT之前，名称和类型已经存在。

Answer 2

提交表单时，您必须阻止默认操作。

在您的assignusers()函数上，将此e.preventDefault()添加到开头

function assignusers(e){
    e.preventDefault();
    // Rest of your code here
    ...
}

Answer 3

您将需要编辑和重新排列代码，如下所示。...

未经测试...

<?php
$_SESSION['login_user'];

if(isset($_POST['edituser']) && $_POST['edituser']=="editUsers"){
    if($_SESSION['login_user']=='admin') {
       $sql = "UPDATE outofstock set name='".$name."',type='".$type."' WHERE id=".$_POST['userId'];
       $result = $db_handle->executeUpdate($sql);
       $redirectUrl="outofstocklist.php";

    } else { 

    $sqlnumrow = "SELECT * FROM outofstock WHERE names = '".$name."' AND department ='".$type."' ";
    $numrow = $db_handle->count($sqlnumrow );// I don't know what function name is yours to check num rows
    if($numrow !=0){
    echo "name and type already exists";
    } else {

    $sql = "INSERT INTO outofstock (name,type) VALUES ('".$name."','".$type."')";

    $result = $db_handle->executeUpdate($sql);
   $redirectUrl="outofstocklist.php";
   }
 }

}
?>