有一table內含圖片欄位, 圖片資料以 JPEGStream 存成 TStream, 再以TBlobField.LoadFromStream的方式讀入, 由於該table在select時有join其他table, 所以用TUpdateSQL來異動資料, 結果當該圖片欄位值為null, 且沒有異動該欄位時, update的結果發現Delphi產生這樣的sql: update tablename set field_n = xxx, .... picture = 0x 結果picture值變成不是null了, UpdateSQL的參數替換是參考李維的書: procedure SetParams(FUpdateSQL: TUpdateSQL; DeltaDS: TClientDataSet; UpdateKind: TUpdateKind); var I: Integer; Old: Boolean; Param: TParam; PName: string; Field: TField; Value: Variant; begin if not Assigned(FUpdateSQL.DataSet) then Exit; with FUpdateSQL.Query[UpdateKind] do begin for I := 0 to Params.Count - 1 do begin Param := Params[I]; PName := Param.Name; Old := CompareText(Copy(PName, 1, 4), 'OLD_') = 0; if Old then System.Delete(PName, 1, 4); Field := DeltaDS.FindField(PName); if not Assigned(Field) then Continue; if Old then Param.AssignFieldValue(Field, Field.OldValue) else begin Value := Field.NewValue; if VarIsEmpty(Value) then begin Value := Field.OldValue; end; Param.AssignFieldValue(Field, Value); end; end; end; end;