How to check if a row exists compared to another value - php

Question

I am not sure how to go about this in PHP & MySQL;
But basically, I just want to check to see if a row exists in a table, and if it does, return a error, example:
$exists = MYSQL CODE TO CHECK HOW MANY ROWS INCLUDE BADGE_ID
if($exists >= 1)
{
$errors[] = "Exists.";
}
Something like that, because I'm coding a small shop script and I want it to check to make sure that they don't already have the badge_id. Structure of the db is user_id and badge_id (user_id = 1, badge_id = 1; for an example)

Answer 1

//Mysql
$res = mysql_query("YOUR QUERY");
if(mysql_num_rows($res) > 0) {
$errors[] = "Exists.";
}
//PDO
$query = $db->prepare("YOUR QUERY");
$ret = $query->execute();
if($ret && $query->rowCount() > 0) {
$errors[] = "Exists.";
}

Answer 2

for this query as
$query=mysql_query("SELECT * from table WHERE userid = 1 AND badgeid = 1");
and in php
if(mysql_num_rows($query)>0){
// whatever you want if match found
}else{
echo "No match Found".
}

Answer 3

$sql = "SELECT COUNT(*) FROM `table_name` WHERE `user_id` = '1' AND `badge_id` = '1' "
$exists = mysql_query($sql) ;
if(mysql_num_rows($exists) >= 1) {
$errors[] = "Exists.";
}else {
// doesn't exists.
}

Answer 4

Try using PDO instead of the old mysql_query() functions for they are deprecated since PHP 5.5.
For a simple query:
$slcBadge = $con->query('SELECT badge_id FROM badges');
if ($slcBadge->rowCount() > 0) {
$errors[] = 'Exists.';
}
Or if you want to fetch all rows from a single user:
$sqlBadge = 'SELECT id_badge FROM badges WHERE id_user = :idUser';
$slcBadge = $con->prepare($sqlBadge);
$slcBadge->bindParam(':idUser', $idUser, PDO::PARAM_INT);
$slcBadge->execute();
if ($slcBadge->rowCount() > 0) {
$errors[] = 'Exists.';
}
Notice that in the second piece of code I used prepare() and execute() rather than query(). This is to protect you query from SQL injection. By using prepare() you fix the construct of your query so if a user enters a query string as a value, it will not be executed. You only need to prepare a query if a user can enter a value which will be used in your query, otherwise query() will do just fine. Check out the injection link for more detailed info.

Answer 5

Your version of PHP is important:
mysql_* functions are deprecated as of 5.4, and
Removed as of 5.5
It is advised to either implement PDO or Mysqli
mysql:
This extension is now deprecated, and deprecation warnings will be generated when connections are established to databases via mysql_connect(), mysql_pconnect(), or through implicit connection: use MySQLi or PDO_MySQL instead
Dropped support for LOAD DATA LOCAL INFILE handlers when using libmysql. Known for stability problems
Added support for SHA256 authentication available with MySQL 5.6.6+
For reference please see the changelog
Structuring your Query
First of all I'm assuming you are indexing your fields correctly refer to this article I posted on Stack Exchange.
Second of all you need to consider efficiency depending on the volume of this table: doing a SELECT * is bad practice when you only need to count the records - mysql will cache row counts and make your SELECT Count(*) much faster. with indexes this is furthermore efficient.
I would simply consider something along the line of this:
$dsn = 'mysql:host=127.0.0.1;dbname=DATABASE';
$db = new PDO($dsn, 'username', 'password', array(
PDO::MYSQL_ATTR_INIT_COMMAND => 'SET NAMES \'UTF8\''
));
NOTE:
where host=127.0.0.1 if your user has been granted access via localhost then you need this to state localhost - or grant the user privileges to 127.0.0.1
NOTE:
with SET NAMES there is also a bug with the PDO driver from 5.3 (I believe) whereby an attacker can inject nullbytes and backspace bytes to remove slashing to then inject the query.
Quick example:
// WARNING: you still need to correctly sanitize your user input!
$query = $db->prepare('SELECT COUNT(*) FROM table WHERE user_id = ? AND badge_id = ?');
$query->execute(array((int) $userId, (int) $badgeId));
$total = $query->fetchAll();

Answer 6

$result = mysql_query("SELECT COUNT(*) FROM table WHERE userid = 1 AND badgeid = 1 LIMIT 1") or die(mysql_error());
if (mysql_result($result, 0) > 0)
{
echo 'exist';
}
else
{
echo 'no';
}