我怎样才能在MySQL数据库表中找不到数据的php代码？

Question

I am so sorry mybe it is a silly question but as I am new in web language and php I dont know how to solve this problem.

I have a code which is getting ID from user and then connecting to MySQL and get data of that ID number from database table and then show on webpage.

But I would like to what should I add to this code if user enter an ID which is not in table of database shows a message that no data found.

Here is my code:

<?php

//connect to the server
$connect = mysql_connect ("localhost","Test","Test") ;

//connection to the database
mysql_select_db ("Test") ;

//query the database
$ID = $_GET['Textbox'];
$query = mysql_query (" SELECT * FROM track WHERE Code = ('$ID') ");

//fetch the results / convert results into an array
$ID = $_GET['Textbox'];

WHILE($rows = mysql_fetch_array($query)) :

     $ID = 'ID';

  echo "<p style=\"font-color: #ff0000;\"> $ID </p>";


  endwhile;

?>

Thank You.

Sorry if it is so silly question.

Answer 1

You should use PDO (great tutorial here: http://wiki.hashphp.org/PDO_Tutorial_for_MySQL_Developers ). This way, you can develop safer applications easier. You need to prepare the ID before inserting it to the query string, to avoid any user manipulation of the mysql query (it is called sql injection, guide: http://www.w3schools.com/sql/sql_injection.asp ).

The main answer to your question, after getting the results, you check if there is any row in the result, if you got no result, then there is no such an ID in the database. If you use PDO statements $stmt->rowCount();.

$db = new PDO('mysql:host=localhost;dbname=testdb;charset=utf8', 'username', 'password');

$stmt = $db->prepare("SELECT * FROM table WHERE Code=?");
$stmt->bindValue(1, $id, PDO::PARAM_INT); // or  PDO::PARAM_STR
$stmt->execute();

$row_count = $stmt->rowCount();

if ($row_count > 0) {
    $results = $stmt->fetchAll(PDO::FETCH_ASSOC);
    //results are in $results
} else {
    // no result, no such an ID, return the error to the user here.
}

Another reason to not use mysql_* functions: http://php.net/manual/en/migration55.deprecated.php