我如何检查mysql表的唯一值，并使用php将其更新一次

问题描述

我只想更新mysql表一次.如果要再次更新，则应显示消息"ID已在使用中，请登录"

I want to update mysql table but only once. If you want to update it again it should give message "ID Already in Use, Pls login"

<?php 
If(isset($_POST['login'])){
$Pin=$_GET['pin'];
$ID =$_POST['ID'];
if($Pin!=''){
$result = mysql_query("SELECT * FROM pin WHERE Pin  = '$Pin'");
$test = mysql_fetch_array($result);

mysql_query("UPDATE pin SET appid ='$num' WHERE Pin= '$Pin'")
            or die(mysql_error()); 

header("location:compet_applicant.php");
}
}

?>   

推荐答案

我认为您应该再添加一个field，例如:number_update到您的pin表中.默认值为0第一次更新时，其值为1，您可以检查该值，如果它是1，将警告ID Already in Use, Pls login.如果是0，请允许更新

I think you should add one more field like: number_update into your pin table first. Default value is 0First time update, it will have value is 1 and you could check that value,if it is 1, will alert ID Already in Use, Pls login. If it is 0, allow to update

$result = mysql_query("SELECT * FROM pin WHERE Pin  = '$Pin'");
$test = array();
while ($row = mysql_fetch_array($result)) {
    $test[] = array_map('utf8_encode', $row);
}

if($test["number_update"] == 1) { //Checking already updated
    //Notify user that they have already updated
} else {
    mysql_query("UPDATE pin SET appid ='$num' WHERE Pin= '$Pin'")
        or die(mysql_error());
}

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