如果返回 True mysql php，如何查询唯一值并更新同一表中的另一个字段

Question

I want to update mysql table pin if Pin field value is the same as the user input pin.In this case, I want to update appid field in the pin table once the the select query returns true.

<?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");
}
}
              
?>   

Answer 1

I think you should add one more field like: number_update into your pin table first. Default value is 0 First 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());
}

Answer 2

<?php
if (isset($_POST['login'])) {
    $Pin = $_GET['pin'];
    $ID  = $_POST['ID'];
    if ($Pin != '') {
        $result = mysql_query("SELECT * FROM pin WHERE Pin  = '$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',number_update = 1 WHERE Pin= '$Pin'") or die(mysql_error());
        }

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

Add one more field "number_update" in your database table as suggested by Mr. Neo and replace your code with the above code.

Answer 3

There should be a log table that record each updation of tables. If the record found then system should prevent further updation for that particular record.

    <?php 
    If(isset($_POST['login'])){
    $Pin=$_GET['pin'];
    $ID =$_POST['ID'];
    if($Pin!=''){
    $update_count = mysql_query("SELECT * FROM Audit_Table_Update WHERE Field_name  = 'Pin' and field_value='$pin');

if(!mysql_num_rows($update_count)){

    $result = mysql_query("SELECT * FROM pin WHERE Pin  = '$Pin'");
    $test = mysql_fetch_array($result);

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

    mysql_query("INSERT INTO AUDIT_TABLE_UPDATES (TABLE_NAME, FIELD_NAME, FIELD_VALUE,TIME_UPDATED) VALUES('Pin','appid',$num,systemtime)")
                or die(mysql_error()); 

    header("location:compet_applicant.php");
    } // end if update count
    }
    }
    ?>