How can I insert the php code to prevent duplicate entry in mysql?

Question

I need to prevent duplicate student number in my SQL database. I don't know where to insert the php code to do that.

/*
* Following code will create a new product row
* All product details are read from HTTP Post Request
*/

// array for JSON response
$response = array();

// check for required fields
if (isset($_POST['name']) && isset($_POST['studnum']) && isset($_POST['password'])) {

$name = $_POST['name'];
$studnum = $_POST['studnum'];
$password = $_POST['password'];

// include db connect class
require_once __DIR__ . '/db_connect.php';

// connecting to db
$db = new DB_CONNECT();

// mysql inserting a new row
$result = mysql_query("INSERT INTO products(name, studnum, password)     VALUES('$name','$studname', '$password')");

// check if row inserted or not
if ($result) {
    // successfully inserted into database
    $response["success"] = 1;
    $response["message"] = "Product successfully created.";

    // echoing JSON response
    echo json_encode($response);
} else {
    // failed to insert row
    $response["success"] = 0;
    $response["message"] = "Oops! An error occurred.";

    // echoing JSON response
    echo json_encode($response);
}


} 
else
{
// required field is missing
$response["success"] = 0;
$response["message"] = "Required field(s) is missing";

// echoing JSON response
echo json_encode($response);
}
?>

please ignore the comments in the code since i only edit it thanks a lot — pakersgalore
– pakersgalore, Commented Aug 19, 2013 at 10:48

M Shahzad Khan · Accepted Answer · 2013-08-19 11:09:26Z

2

add unique to some of the columns which you think can make unique record, then

$result = mysql_query("INSERT INTO products(name, studnum, password)     VALUES('$name','$studname', '$password') ON DUPLICATE KEY UPDATE studnum=VALUES(studnum)");

It will update the record and prevent you from showing duplicate error.

answered Aug 19, 2013 at 11:09

M Shahzad Khan

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1 Comment

Sébastien Gicquel Over a year ago

You’re right : Its important to avoid MySQL error. In most cases, Php will ignore it but with ajax, the MySQL error could be an issue when using a callback function.

Taemyr · Accepted Answer · 2013-08-19 10:58:29Z

0

Run the following SQL statement in your db

alter table products add unique index(studnum);

This will tell mySQL that the studnum field should be unique and will cause it to give an error message if a duplicate is created.

answered Aug 19, 2013 at 10:58

Taemyr

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