Is using a SELECT COUNT(*) query more efficient than a SELECT * query for checking if a username is already registered in PHP?

Using a SELECT COUNT(*) query is more efficient than a SELECT * query for checking if a username is already registered in PHP because it only retrieves the count of rows that match the specified condition, rather than retrieving all the columns of the matching rows. This can significantly reduce the amount of data transferred between the database and the PHP script, resulting in faster execution times. 

<?php
$username = "example_username";
$query = "SELECT COUNT(*) FROM users WHERE username = :username";
$stmt = $pdo->prepare($query);
$stmt->bindParam(':username', $username);
$stmt->execute();
$count = $stmt->fetchColumn();

if($count > 0) {
    echo "Username is already registered.";
} else {
    echo "Username is available.";
}
?>

Keywords

SELECT COUNT(*) SELECT * username registration efficiency

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