原想若資料有異動時, SQLClientDataSet.Delta.Fields會有值, 若無做異動修改, 則會是NULL, 所以根據這想法 撰寫如下的來動態產生Update 的SQL COMMAND,  判斷Field.isNull表未異動,就略過, 現在發現若異動後的是null, 就會被我略過, 沒有更新到,  有沒有什麼方式, 該我知道這Field是我異動成null, 而非未曾異動的null?? 或有其他方式可以關連原SQLClientDataSet知道修改後的值 或有其他解決方法??     

procedure SQLClientDataSetBeforeUpdateRecord(Sender: TObject;
  SourceDS: TDataSet; DeltaDS: TCustomClientDataSet;
  UpdateKind: TUpdateKind; var Applied: Boolean);
var SQLSTR,Wheres,FieldSTR,TableName:string;
    i:integer;qUpQuery:TSQLQuery;
begin
  Applied:=false;
  qUpQuery:=TSQLQuery.Create(Self);  
  qUpQuery.SQLConnection:=SQLConnection;
  qUpQuery.SQL.Clear;
  TableName:='TEST';
  if UpdateKind= ukModify then begin
     SQLSTR:='';
     FOR i := 0 TO DeltaDS.FieldCount -1 do begin
       FieldSTR:=DeltaDS.Fields.Fields[i].FieldName;  
       if pfInUpdate in SQLClientDataSet.Fields.FindField(FieldSTR).ProviderFlags then begin
          if ( not DeltaDS.Fields.Fields[i].IsNull) then begin
             if SQLSTR='' then
                SQLSTR:=' update '   TableName  ' set ' FieldSTR '=:' FieldSTR
             else
                SQLSTR:= SQLSTR ',' FieldSTR '=:' FieldSTR;
          end;
       end;
     //產生where 條件
       if ( pfInWhere in SQLClientDataSet.Fields.FindField(FieldSTR).ProviderFlags ) then begin
           if VarIsNull(DeltaDS.Fields.FieldByName(FieldSTR).OldValue) then
              if wheres='' then wheres:=' WHERE ' FieldSTR ' IS NULL ' else
                 wheres:=wheres ' AND ' FieldSTR ' IS NULL '
           else
             if wheres='' then wheres:=' WHERE ' FieldSTR '=:OLD_' FieldSTR else
                wheres:=wheres ' AND ' FieldSTR '=:OLD_' FieldSTR;
        end;
     end;
  end;      qUpQuery.SQL.Add(SQLSTR wheres);      //設定params開始
  FOR i := 0 TO DeltaDS.FieldCount -1 do begin
    FieldSTR:=DeltaDS.Fields.Fields[i].FieldName;
    if UpdateKind in [ukModify] then begin
      if ( not DeltaDS.Fields.Fields[i].IsNull) and
          ( pfInUpdate in SQLClientDataSet.Fields.FindField(FieldSTR).ProviderFlags ) then begin
          qUpdateQuery.Params.ParamByName(FieldSTR).DataType:=DeltaDS.Fields.FieldByName(FieldSTR).DataType;
          qUpdateQuery.Params.ParamByName(FieldSTR).ParamType:=ptInput;
          qUpdateQuery.Params.ParamByName(FieldSTR).Value:=DeltaDS.FieldByName(FieldSTR).Value;
       end;
    end;
    if UpdateKind in [ukModify] then begin
       if ( pfInWhere in SQLClientDataSet.Fields.FindField(FieldSTR).ProviderFlags ) then begin
           if VarIsNull(DeltaDS.Fields.FieldByName(FieldSTR).OldValue) then
          else begin
            OldFieldSTR:='OLD_' FieldSTR;
            qUpdateQuery.Params.ParamByName(OldFieldSTR).DataType:=DeltaDS.Fields.FieldByName(FieldSTR).DataType;;
            qUpdateQuery.Params.ParamByName(OldFieldSTR).ParamType:=ptInput;
            qUpdateQuery.Params.ParamByName(OldFieldSTR).Value:=DeltaDS.Fields.FieldByName(FieldSTR).OldValue;
          end;
       end;
    end;    end;        

發表人 -

You should check against Unassigned, not Null.

procedure SQLClientDataSetBeforeUpdateRecord(Sender: TObject;
  SourceDS: TDataSet; DeltaDS: TCustomClientDataSet;
  UpdateKind: TUpdateKind; var Applied: Boolean);

在BeforeUpdateRecord事件中不是有SourceDS，sourceDS代表原始資料，你用SourceDS與DeltaDS兩邊對比不就知道了 混心雜欲 棄修身~唉

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唉~