Database - handling of unique constraint violation

Question

I have a user creation screen that takes various user details along with first name and mobile number. I have a corresponding USER table in which the First Name and the Mob

Answer 1

Here's a PHP version of eggyal's answer, using MySQLi.

// Error: 1062 SQLSTATE: 23000 (ER_DUP_ENTRY)               Message: Duplicate entry '%s' for key %d
// Error: 1586 SQLSTATE: 23000 (ER_DUP_ENTRY_WITH_KEY_NAME) Message: Duplicate entry '%s' for key '%s'
if($mysqli->errno === 1062 || $mysqli->errno === 1586)
{
    if(preg_match("/Duplicate entry '(.*)' for key '(.*)'/", $mysqli->error, $matchArray) === 1)
    {
        $duplicatedValue = $matchArray[1];
        $uniqueKeyName = $matchArray[2];

        if(!($stmt = $mysqli->prepare('SELECT COLUMN_NAME'
                                    . '  FROM INFORMATION_SCHEMA.KEY_COLUMN_USAGE'
                                    . ' WHERE CONSTRAINT_SCHEMA = ?'
                                    . '   AND CONSTRAINT_NAME = ?')))
        {
            die;    // Error? Check $mysqli->errno and $mysqli->error;
        }
        $schemaName = // Name of the schema (string).
        if(!$stmt->bind_param('ss', $schemaName, $uniqueKeyName))
        {
            die;    // Error? Check $mysqli->errno and $mysqli->error;
        }
        if(!$stmt->execute())
        {
            die;    // Error? Check $mysqli->errno and $mysqli->error;
        }
        $res = $stmt->get_result();
        if(!$res)
        {
            die;    // Error? Check $mysqli->errno and $mysqli->error;
        }
        $row = $res->fetch_assoc();
        if($row === null)
        {
            die;    // No results?
        }
        $columnName = $row['COLUMN_NAME'];
    }
}