一个很奇怪的问题，大家来帮帮忙。。。

一个存储过程，我用程序执行存储过程查询出一个dataTable里面是71条数据，但是我直接在数据库中执行的话，返回的数据条数是79条，这个问题好奇怪啊上代码： public static DataTable WhiteCardReplacementData(string beginDate, string enddate,string dateType)
        {
            DataTable dt = new DataTable();
            SqlParameter[] para = new SqlParameter[] { 
                new SqlParameter("@BeginDate",beginDate),
                new SqlParameter("@EndDate",enddate),
                new SqlParameter("@DateType",dateType)
            };
            try
            {
                dt = SqlHelper.ExecuteDataTable(SqlHelper.ConnectionString, CommandType.StoredProcedure, "usp_Report_WhiteCardData", para);
                return dt;
            }
            catch (Exception e)
            {
                
                throw;
            }
        }//Sqlhelper中的代码：
 public static DataTable ExecuteDataTable(string connectionString, CommandType commandType, string commandText, params SqlParameter[] commandParameters)
        {
            if (connectionString == null || connectionString.Length == 0) throw new ArgumentNullException("connectionString");            // Create & open a SqlConnection, and dispose of it after we are done
            using (SqlConnection connection = new SqlConnection(connectionString))
            {
                connection.Open();                // Call the overload that takes a connection in place of the connection string
                return ExecuteDataTable(connection, commandType, commandText, commandParameters);
            }
        }public static DataTable ExecuteDataTable(SqlConnection connection, CommandType commandType, string commandText, params SqlParameter[] commandParameters)
        {
            if (connection == null) throw new ArgumentNullException("connection");            // Create a command and prepare it for execution
            SqlCommand cmd = new SqlCommand();
            bool mustCloseConnection = false;
            PrepareCommand(cmd, connection, (SqlTransaction)null, commandType, commandText, commandParameters, out mustCloseConnection);            // Create the DataAdapter & DataSet
            using (SqlDataAdapter da = new SqlDataAdapter(cmd))
            {
                DataTable dt = new DataTable();
                // Fill the DataSet using default values for DataTable names, etc
                da.Fill(dt);                // Detach the SqlParameters from the command object, so they can be used again
                cmd.Parameters.Clear();                if (mustCloseConnection)
                    connection.Close();                // Return the datatable
                return dt;
            }
        }
private static void PrepareCommand(SqlCommand command, SqlConnection connection, SqlTransaction transaction, CommandType commandType, string commandText, SqlParameter[] commandParameters, out bool mustCloseConnection)
        {
            if (command == null) throw new ArgumentNullException("command");
            if (commandText == null || commandText.Length == 0) throw new ArgumentNullException("commandText");            // If the provided connection is not open, we will open it
            if (connection.State != ConnectionState.Open)
            {
                mustCloseConnection = true;
                connection.Open();
            }
            else
            {
                mustCloseConnection = false;
            }            // Associate the connection with the command
            command.Connection = connection;            // Set the command text (stored procedure name or SQL statement)
            command.CommandText = commandText;            // If we were provided a transaction, assign it
            if (transaction != null)
            {
                if (transaction.Connection == null) throw new ArgumentException("The transaction was rollbacked or commited, please provide an open transaction.", "transaction");
                command.Transaction = transaction;
            }            // Set the command type
            command.CommandType = commandType;            // Attach the command parameters if they are provided
            if (commandParameters != null)
            {
                AttachParameters(command, commandParameters);
            }
            return;
        }
附上SQL语句：select '邮编:'+ZipCode as ZipCode,Address,Customer 
from dbo.WhiteCardReplacementData
where convert(varchar(10),UpdateDate,120) between @BeginDate and @EndDate
and Customer!=''谢谢啦