What are the advantages of using Count(*) with a limit of 1 over mysql_num_rows() in PHP login scripts?

When checking if a user exists in a database during a login process, using `COUNT(*)` with a limit of 1 is more efficient than using `mysql_num_rows()`. This is because `COUNT(*)` simply returns the number of rows that match the query, while `mysql_num_rows()` fetches and stores all the rows in memory before counting them. Therefore, using `COUNT(*)` with a limit of 1 reduces memory usage and improves performance in PHP login scripts. 

// Using COUNT(*) with a limit of 1 to check if a user exists in the database
$query = "SELECT COUNT(*) FROM users WHERE username = '$username' LIMIT 1";
$result = mysqli_query($connection, $query);
$row = mysqli_fetch_array($result);

if ($row[0] > 0) {
    // User exists
} else {
    // User does not exist
}

Keywords

Count(*) limit mysql_num_rows() PHP login script

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