图片到数据库的存入和取出问题(30分)

var
JPEGImage: TJPEGImage;
Stream: TMemoryStream;
str:Tmemorystream;
begin
fmDataModVod.ClientDatSetMovie.Edit;
if image1.Picture.Graphic<>nil then //把img里的图片用流形式保存到数据库
begin
str:=Tmemorystream.Create;
image1.Picture.Graphic.SaveToStream(str);
str.Position:=0;
Tblobfield(fmDataModVod.ClientDatSetMovie.FieldByName('pic')).loadfromstream(str);
fmDataModVod.ClientDatSetMovie.Post;
fmDataModVod.ClientDatSetMovie.ApplyUpdates(0);
str.Free;
end
else
begin
fmDataModVod.ClientDatSetMovie.FieldByName('pic').value:=null;
end;
--------------------------------------------------------------------------
为什么在ApplyUpdate的时候会出错？有没有比这更好更有效率的方法存入数据库？
这里的POST和ApplyUpdate各有什么作用？区别在哪？
由于组件的不同，操作也有可能不同，希望尽可能给出相同组件的操作，或是其他组件与此组件的区别与相同点为谢。

补充一下出错的错误信息：
Project1.exe raised exception class EDataBaseError With message' Cannot create new transaction because capacity was exceeded.'. Process stopped. Use Step or Run to continue.

ApplyUpdates是缓存概念，它把缓存里的数据提交数据库；Post是把对记录的修改操作提交到数据库，当不用缓存技术时，它将直接正式提交数据。
ApplyUpdates一般与事务概念一起应用，便于一次提交或回滚数据。一般的使用格式大致为：
DataBaseAlias.StartTransaction;
try
Query1.edit;
....
Query1.post;//提交数据
Query1.ApplyUpdates;//提交缓存
Query1.CommitUpdates;//清理缓存
//Query的UpdateObject属性必须指定为UpdateSQL组件，即启动缓存操作

DatabaseAlias.Commit;
except
DatabaseAlias.RollBack;
end;

我用的DBExpress组件，用了SQLConnecation，SQLDataSet，ClientDataset，Query等，我该对哪个进行事务操作？

fmDataModVod.ClientDatSetMovie.First;
if image1.Picture.Graphic<>nil then //把img里的图片用流形式保存到数据库
begin
if not fmDataModVod.SQLConnVod.InTransaction then
begin
TD.TransactionID := 1;
TD.IsolationLevel := xilREADCOMMITTED;
fmDataModVod.SQLConnVod.StartTransaction(TD); //这句出错
try
fmDataModVod.ClientDatSetMovie.Edit;
str:=Tmemorystream.Create;
image1.Picture.Graphic.SaveToStream(str);
str.Position:=0;
Tblobfield(fmDataModVod.ClientDatSetMovie.FieldByName('pic')).loadfromstream(str);
fmDataModVod.ClientDatSetMovie.Post;
fmDataModVod.ClientDatSetMovie.ApplyUpdates(0);
fmDataModVod.SQLConnVod.Commit(TD);
str.Free;
except
fmDataModVod.SQLConnVod.Rollback(TD);
raise;
end;
end;
end
else
begin
fmDataModVod.ClientDatSetMovie.FieldByName('pic').value:=null;
end;

出错信息如下：
Project Project1.exe raised exception class EDatabaseError with message'. Cannot create new transaction because capacity was exceeded.'. Process stopped. Use Step or Run to continue.

谁来帮我看看，分析一下。

还是这个问题，再次发问：
procedure TFmAddMovie.BitBtn1Click(Sender: TObject);
var
MyJPEG :TJPEGImage;
MS: TMemoryStream;
begin
MyJPEG := TJPEGImage.Create;
try
with MyJPEG do
begin
Assign(Image1.Picture.Graphic);
MS:=TMemoryStream.create;
SaveToStream(MS);
MS.Position:=0;

fmDataModVod.SQLQryMovie.Close;
fmDataModvod.SQLQryMovie.SQL.Clear;
fmDataModVod.SQLQryMovie.SQL.Add('update [MOVIES] set [PIC]= 1 where [MOVIES]= 2 ');
fmDataModVod.SQLQryMovie.ParamByName('p1').LoadFromFile('D:/test.bmp',ftBlob);
//fmDataModVod.SQLQryMovie.ParamByName('p1').AsBlob := 'd:/test.bmp';
//fmDataModVod.SQLQryMovie.FieldbyName('p1').LoadFromStream(MS);
//这上面有三条语句，倒底用哪条操作是正确的？
fmDataModVod.SQLQryMovie.ParamByName('P2').AsString := DBEdit1.Text;
try
fmDataModVod.SQLQryMovie.EXECSQL(false);
messagebox(getactivewindow(),'图像保存完毕！','保存',mb_ok);
Image1.Picture.LoadFromFile('');
except
Application.MessageBox('图片保存错误！','系统提示：',mb_ok);
end;

//fmDataModVod.SQLQryMovie.Edit;
//TBlobField(fmDataModVod.SQLQryMovie.FieldbyName('pic')).LoadFromStream(MS);
//fmDataModVod.SQLQryMovie.Post;
end;
finally
MyJPEG.Free;
end;
end;

分我还会再加的，尽我所有。

to bjaman,
你好，你所说的我没有成功，你能不能以我此例，给我做一个例子？
我将的感谢，并会多付分表示感谢。

这篇文章你参考一下吧
DELPHI存取JPEG文件到SQL Server数据库
高红岩(ghyghost)
近日笔者书写一个小型的学生管理系统时，需要用到ADO控件存取SQL Server数据库图片，查看资料发现基本都是针对BMP文件进行操作(巨增数据库大小)，但发现了★eagletian★高手翻译的ADO英文技术文档，里面涉及到了数据库存取JPEG文件的关键技术，在win98+sql server桌面版中测试通过，运行良好，现于源码公开如下：
unit Unit1;

interface

uses
Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
ExtCtrls, DBCtrls, Grids, DBGrids, Db, ADODB,jpeg, StdCtrls,dbtables;
{一定要USES JPEG单元,使能存储JPG文件格式}
type
TForm1 = class(TForm)
DataSource1: TDataSource;
ADOQuery1: TADOQuery;
DBGrid1: TDBGrid;
DBNavigator1: TDBNavigator;
Image1: TImage;
savebutton: TButton;
showbutton: TButton;
OpenDialog1: TOpenDialog;
ADOQuery1id: TIntegerField;
ADOQuery1pic: TBlobField;
procedure savebuttonClick(Sender: TObject);
procedure showbuttonClick(Sender: TObject);
procedure DBNavigator1Click(Sender: TObject; Button: TNavigateBtn);
private
{ Private declarations }
public
{ Public declarations }
end;

var
Form1: TForm1;

implementation

{$R *.DFM}

function JpegStartsInBlob(PicField:TBlobField):integer;
var
ghy: TADOBlobstream;
buffer:Word;
hx: string;
begin
Result := -1;
ghy := TADOBlobstream.Create(PicField, bmRead);
try
while (Result = -1) and (ghy.Position + 1 < ghy.Size) do
begin
ghy.ReadBuffer(buffer, 1);
hx:=IntToHex(buffer, 2);
if hx = ’FF’ then begin
ghy.ReadBuffer(buffer, 1);
hx:=IntToHex(buffer, 2);
if hx = ’D8’ then Result := ghy.Position - 2
else if hx = ’FF’ then
ghy.Position := ghy.Position-1;
end; //if
end; //while
finally
ghy.Free
end; //try
end;


procedure TForm1.savebuttonClick(Sender: TObject);
var
picstream:tadoblobstream;
begin
adoquery1.edit;
picstream:=tadoblobstream.Create(tblobfield(adoquery1.fields[1]),bmWrite);
if form1.opendialog1.execute then
begin
picstream.LoadFromFile(opendialog1.filename);
picstream.Position:=0;
adoquery1.edit;
tblobfield(adoquery1.Fields[1]).loadfromstream(picstream);
adoquery1.post;
end;


end;

procedure TForm1.showbuttonClick(Sender: TObject);
var
ghy:TADOBlobstream;
pic:tjpegimage;
begin
ghy := TADOBlobstream.Create(Adoquery1pic, bmRead);
try
ghy.Seek(JpegStartsInBlob(Adoquery1pic),soFromBeginning);
Pic:=TJpegImage.Create;
try
Pic.LoadFromStream(ghy);
Image1.Picture.Graphic:=Pic;
finally
Pic.Free;
end;
finally
ghy.Free
end;
end;

procedure TForm1.DBNavigator1Click(Sender: TObject; Button: TNavigateBtn);
begin
if button in [nbFirst, nbPrior, nbNext, nbLast] then showbutton.Click;
end;

end.

如果数据库中要存储的是BMP文件，则在procedure TForm1.showbuttonClick(Sender: TObject);过程中代码更改如下即可存储显示BMP文件格式的操作。
procedure TForm1.showbuttonClick(Sender: TObject);
var
ghy:TADOBlobstream;
pic:tbitmap;
begin
ghy := TADOBlobstream.Create(Adoquery1pic, bmRead);
try
{ ghy.Seek(JpegStartsInBlob(Adoquery1pic),soFromBeginning);}
Pic:=Tbitmap.Create;
try
Pic.LoadFromStream(ghy);
Image1.Picture.Graphic:=Pic;
finally
Pic.Free;
end;
finally
ghy.Free
end;
end;

谢谢app2001,小妹正在到处找它！

这里可以找到答案：
http://www.delphibbs.com/delphibbs/dispq.asp?lid=2234684

不错！！！厉害！！呵呵