随机取数据

Question

select * from table order by newid()

/// <summary>
        /// 随机从数据库中取N条记录
        /// </summary>
        /// <param name="commandText"></param>
        /// <param name="nTop">返回的记录数</param>
        /// <param name="nRecordCount">满足条件的总记录数</param>
        /// <returns></returns>
        public static DataSet ExecuteDataSetRandom(string commandText, int nTop, int nRecordCount,params DbParameter[]parm)
        {
            return ExecuteDataSetRandom(CommandType.Text, commandText, nTop, nRecordCount,parm);
        }
        public static DataSet ExecuteDataSetRandom(CommandType commandType, string commandText,int nTop,int nRecordCount, params DbParameter[] commandParameters)
        {
         
            if (ConnectionString == null || ConnectionString.Length == 0) throw new ArgumentNullException("ConnectionString");

            // 创建并打开数据库连接对象,操作完成释放对象.

            //using (DbConnection connection = (DbConnection)new System.Data.SqlClient.SqlConnection(ConnectionString))
            using (DbConnection connection = Factory.CreateConnection())
            {
                connection.ConnectionString = ConnectionString;
                connection.Open();

                // 调用指定数据库连接字符串重载方法.
                //return ExecuteDataset(connection, commandType, commandText, commandParameters);
               // 预处理
                DbCommand cmd = Factory.CreateCommand();
                bool mustCloseConnection = false;
                PrepareCommand(cmd, connection, (DbTransaction)null, commandType, commandText, commandParameters, out mustCloseConnection);

                // 创建DbDataAdapter和DataSet.
                using (DbDataAdapter da = Factory.CreateDataAdapter())
                {
                    da.SelectCommand = cmd;
                    DataSet ds = new DataSet();
                    Random rdm = new Random();
                    int nStart = 0;
                    if(nRecordCount>nTop)
                        nStart=rdm.Next(nRecordCount - nTop);
                    if (nStart < 0)
                        nStart = 0;
                    // 填充DataSet.
                    da.Fill(ds,nStart,nTop,"tab0");

                    m_querycount++;

                    cmd.Parameters.Clear();

                    if (mustCloseConnection)
                        connection.Close();

                    return ds;
                }
            }

        }这两种方法哪儿个好？哪个快？

---

无