根据DELTA自动生成SQL语句

根据DELTA自动生成SQL语句上传客户端的CLIENTDATASET.delta到服务器的clientdataset.data，服务端解析clientdataset的数据生成相应的SQL语句。相对于直接调用datasetprovider.applyupdates()方法提交数据而言，前者的可控性更强，对于某些要求灵活性很强的场合，前者可能是必须的提交方式。procedure TBaseService.ApplyUpdates(const Delta: OleVariant; TableName, KeyField: WideString);var  Flag: Boolean;begin  if VarIsNull(Delta) then exit;  with (FParent as TDataServer2) do    begin      cdsDelta.Close;      cdsDelta.Data := Delta;      Flag := cdsDelta.FindField('SYS_STATUS') nil;    end; // with  if Flag then    InnerApplyUpdates2(TableName, KeyField)  else    InnerApplyUpdates(TableName, KeyField);end;  function vartosql(value: Variant): wideString;      var      tmp:widestring;      begin         if (varisnull(Value)) or (varisempty(Value)) then          Result:='NULL'         else          case Vartype(value) of            varDate:            begin              tmp := formatDatetime('yyyy-mm-dd hh:mm:ss', VartoDatetime(Value));              Result:=Quotedstr(tmp);            end;            varString,varOlestr:              Result:=Quotedstr(Trim(Vartostr(Value)));            varboolean:            begin              if Value then                Result:='1'              else                Result:='0';            end;            varSmallint,varInteger,varDouble,varShortInt,varInt64,varLongWord,varCurrency:            begin              Result:=trim(Vartostr(Value));            end;          else              Result:=Quotedstr(Trim(Vartostr(Value)));          end;      end;procedure TBaseService.InnerApplyUpdates(TableName, KeyField: WideString);var  i: integer;  s1, s2: string;  CmdStr: string;  FieldList: TStringList;begin  with (FParent as TDataServer2) do    begin      FieldList := TStringList.Create;      Connection.GetFieldNames(TableName, FieldList);      if not cdsDelta.Active then cdsDelta.Open;      for i := 1 to FieldList.Count do        if cdsDelta.FindField(FieldList[i - 1]) nil then          cdsDelta.FindField(FieldList[i - 1]).Tag := 1;      FieldList.Free;      if cdsDelta.RecordCount > 0 then        begin          cdsDelta.First;          s1 := '';          s2 := '';          while not cdsDelta.Eof do            begin              CmdStr := '';              case cdsDelta.UpdateStatus of                usUnmodified:                  begin                    s2 := VarToSql(cdsDelta[KeyField]);                  end;                usModified:                  begin                    s1 := '';                    for i := 1 to cdsDelta.FieldCount do                     // if (not cdsDelta.Fields[i - 1].IsNull) and (cdsDelta.Fields[i - 1].Tag = 1) then if (cdsDelta.Fields[i-1].NewValue System.Variants.Unassigned and (cdsDelta.Fields[i - 1].Tag = 1) then                        begin                          if s1 = '' then                            s1 := Trim(cdsDelta.Fields[i - 1].FieldName) + ' = ' + VarToSql(cdsDelta.Fields[i - 1].Value)                          else                            s1 := s1 + ',' + Trim(cdsDelta.Fields[i - 1].FieldName) + ' = ' + VarToSql(cdsDelta.Fields[i - 1].Value);                        end;                    if s1 '' then                      begin                        CmdStr := 'Update ' + TableName + ' Set ' + s1 + ' Where ' + KeyField + ' = ' + s2;                      end;                  end;                usInserted:                  begin                    s1 := '';                    s2 := '';                    for i := 1 to cdsDelta.FieldCount do                      if (not cdsDelta.Fields[i - 1].IsNull) and (cdsDelta.Fields[i - 1].Tag = 1) then                        begin                          if s1 = '' then                            begin                              s1 := Trim(cdsDelta.Fields[i - 1].FieldName);                              s2 := VarToSql(cdsDelta.Fields[i - 1].Value);                            end                          else                            begin                              s1 := s1 + ',' + Trim(cdsDelta.Fields[i - 1].FieldName);                              s2 := s2 + ',' + VarToSql(cdsDelta.Fields[i - 1].Value);                            end;                        end;                    if s1 '' then                      begin                        CmdStr := 'Insert into ' + TableName + '(' + s1 + ') Values (' + s2 + ')';                      end;                  end;                usDeleted:                  begin                    s2 := VarToSql(cdsDelta[KeyField]);                    CmdStr := 'Delete ' + TableName + ' Where ' + KeyField + ' = ' + s2;                  end;              end;              if CmdStr '' then Cmd.Execute(CmdStr);              cdsDelta.Next;            end;          cdsDelta.First;          cdsDelta.EmptyDataSet;          cdsDelta.Close;        end;    end;end;