如果Null不起作用，则为SQL Update文本值

Question

I am trying to make it so that a specific value can only be set once, by making it so that i can only be updated or set if it is equal to null. For some reason, the PHP still echoes success even when the value is equal to something like: "Steve". What am I doing wrong?

PHP:

<?php
$dbhandle = mysql_connect($hostname, $username, $password) 
  or die("Unable to connect to MySQL");

//select a database to work with
$selected = mysql_select_db("???????",$dbhandle) 
  or die("Could not select examples");

if(empty($_POST['OrderID']) || empty($_POST['UserName'])){
            echo 'Failed. Fill out all fields.';
        }
else{
        $sql = mysql_query("SELECT * FROM orders WHERE order_id = '".$_POST['OrderID']."' AND LENGTH(accepter_name)= 0");
        $row = mysql_fetch_row($sql); // get the single row.
        echo $row['accepter_name']; // display the value.    

        if($row['accepter_name']==''){ 
            $sql = mysql_query("UPDATE orders SET accepter_name= '".$_POST['UserName']."' WHERE order_id='".$_POST['OrderID']."'");
                    echo "Success";   
        }
        else{
        echo "Failed";
         }
}
mysql_close($dbhandle);
?>

When i check on the database, the accepter name value is changed.

Answer 1

You can use if( mysql_affected_rows($sql) == 1 ) instead of if($sql) because the sql is executed and it's returns no rows affected. So, if you check for affected rows it should return 1 when your sql updated at least one row in your table