private string BuildSql() { if (string.IsNullOrWhiteSpace(Table)) { throw new InvalidOperationException("table name is missing"); } if (FieldNames.Count == 0) { throw new InvalidOperationException("field names are missing"); } return(new StringBuilder() .AppendInsert(Table, TemporaryTable, FieldNames, OutputFields) .Append(" ") .Append(SelectCommand.Build().CommandText) .ToString()); }