using (MySqlConnection connection = new DBConnection().Connect())
{
    using (MySqlCommand command = new MySqlCommand())
    {
        command.Connection = connection;
        command.CommandText = "INSERT IGNORE INTO competition_rounds (round_id, season_id, `name`)
                                             VALUES (@round_id, @season_id, @round_name)";

        command.Parameters.Add("@round_id", MySqlDbType.Int32).Value = round.Id;
        command.Parameters.Add("@season_id", MySqlDbType.Int32).Value = round.seasonId;
        command.Parameters.Add("@round_name", MySqlDbType.VarChar).Value = round.Name;
        command.ExecuteNonQuery();

        return Convert.ToInt32(command.LastInsertedId);
    }
}

instance 1 -> fire round insert -> return 3
instance 2 -> fire round insert -> return 3