有用MyDAC连MySQL的Text或BLOB遭遇32KB文本超大难题的吗？ Delphi / Windows SDK/APIhttp://www.delphi2007.net/DelphiDB/html/delphi_20061221030445196.html
编一个资料库系统，客户强调采用UTF-8编码。
以配合以后的Web系统。
结果发现只有MyDAC支持UTF-8和Unicode。
但是在开发过程中发现，Memo或RichEdit中，
超过32KB的文本，无法存入MySQL数据库，
字段类型无论采用Text,Longtext,blob,longblob都不成。
怀疑是MyDAC本身的问题，用其附带的Text例子，也一样不能超出32KB。
特征解决方案。
试试最新版本的
我试过没问题
1.建表:
Create table t1 (a longtest);
2.写数据:
procedure TForm1.Button1Click(Sender: TObject);
begin
with mySQLQuery1 do
begin
SQL.Text:='insert into t1 values(:ltext)';
Params.ParamByName('ltext').LoadFromFile('D:\t.txt',ftMemo); //t.txt为82K文本文件
ExecSQL;
end;
end;
3.读数据:
var
t:TMemoryStream;
begin
t:=TMemoryStream.Create;
with mySQLQuery1 do
begin
SQL.Text:='select * from t1';
Open;
(FieldByName('a') as TMemoField).SaveToStream(t);
t.Position:=0;
Memo1.Lines.LoadFromStream(t);
end;
t.Free;
end;
我采用的是Table.Append，结果就是没有通过。没想到去试Query。
因为columns太多了，用query太麻烦。
用的MyDAC是MySQL Data Access Components 4.4
不是Scibit MyComponent，
Scibit MyComponent对UTF-8支持不行。
用Query还是一样啊，
Access violation at address 00403287 in module 'DBMan.exe', Read of address 001338B4
PS.
MySQL Server是 5.0版的，测试服务器是Win32版本的，
会不会有问题？
应该与版本没关系(我也用5.0的).
开发C/S结构,除桌面数据库以外(fox/access等)尽量不要用table的方法.要用sql来对数据库操作,对于longtext/blob字段,要用Stream方式
你的
Access violation at address 00403287 in module 'DBMan.exe', Read of address 001338B4
错,要查你的程序是否有内存溢出
另外,你可先写一段测试程序(如我上面的)看看是否为控件的问题
我只用Table作Append，
Update和Del都用Query。
因为column太多了。
试过了，也一样。
看来是控件的问题。
MySQL Data Access Components 4.4
自带的Demos，
用DBGrid+DBNav，写入也是一样的错误。
Demo源码：
Main.dfm
object fmMain: TfmMain
Left = 245
Top = 151
Caption = 'MySQL Data Access Demo - TEXT fields'
ClientHeight = 410
ClientWidth = 593
Color = clBtnFace
Font.Charset = DEFAULT_CHARSET
Font.Color = clWindowText
Font.Height = -11
Font.Name = 'MS Sans Serif'
Font.Style = []
OldCreateOrder = True
Position = poScreenCenter
PixelsPerInch = 96
TextHeight = 13
object Splitter1: TSplitter
Left = 0
Top = 233
Width = 593
Height = 2
Cursor = crVSplit
Align = alTop
end
object DBGrid: TDBGrid
Left = 0
Top = 25
Width = 593
Height = 182
Align = alTop
DataSource = DataSource
TabOrder = 0
TitleFont.Charset = DEFAULT_CHARSET
TitleFont.Color = clWindowText
TitleFont.Height = -11
TitleFont.Name = 'MS Sans Serif'
TitleFont.Style = []
end
object ToolBar: TPanel
Left = 0
Top = 0
Width = 593
Height = 25
Align = alTop
TabOrder = 1
object ToolButton1: TToolButton
Left = 362
Top = 2
Width = 16
Caption = 'ToolButton1'
Style = tbsSeparator
end
object btOpen: TButton
Left = 0
Top = 2
Width = 70
Height = 22
Caption = 'Open'
TabOrder = 0
OnClick = btOpenClick
end
object btClose: TButton
Left = 70
Top = 2
Width = 69
Height = 22
Caption = 'Close'
TabOrder = 2
OnClick = btCloseClick
end
object DBNavigator: TDBNavigator
Left = 139
Top = 2
Width = 220
Height = 22
DataSource = DataSource
TabOrder = 1
end
object btCreate: TButton
Left = 451
Top = 2
Width = 69
Height = 22
Caption = 'Create'
Font.Charset = DEFAULT_CHARSET
Font.Color = clWindowText
Font.Height = -9
Font.Name = 'MS Sans Serif'
Font.Style = [fsBold]
ParentFont = False
TabOrder = 3
OnClick = btCreateClick
end
object btDrop: TButton
Left = 520
Top = 2
Width = 70
Height = 22
Caption = 'Drop'
Font.Charset = DEFAULT_CHARSET
Font.Color = clWindowText
Font.Height = -9
Font.Name = 'MS Sans Serif'
Font.Style = [fsBold]
ParentFont = False
TabOrder = 4
OnClick = btDropClick
end
end
object meComments: TDBMemo
Left = 0
Top = 235
Width = 593
Height = 175
Align = alClient
DataField = 'TextField'
DataSource = DataSource
MaxLength = 65535
ScrollBars = ssBoth
TabOrder = 2
end
object ToolBar1: TToolBar
Left = 0
Top = 207
Width = 593
Height = 26
ButtonHeight = 24
EdgeInner = esNone
EdgeOuter = esNone
TabOrder = 3
object btLoad: TButton
Left = 0
Top = 0
Width = 75
Height = 24
Caption = 'Load from file'
TabOrder = 0
OnClick = btLoadClick
end
object btSave: TButton
Left = 75
Top = 0
Width = 75
Height = 24
Caption = 'Save to file'
TabOrder = 1
OnClick = btSaveClick
end
object ToolButton2: TToolButton
Left = 150
Top = 0
Width = 25
Caption = 'ToolButton2'
Style = tbsSeparator
end
object btClear: TButton
Left = 175
Top = 0
Width = 75
Height = 24
Caption = 'Clear'
TabOrder = 2
OnClick = btClearClick
end
end
object MyConnection: TMyConnection
Database = 'test'
IsolationLevel = ilSerializable
Options.UseUnicode = True
Options.Charset = 'utf8'
Options.KeepDesignConnected = False
Username = 'root'
Password = 'xcvuht8m98qy'
Server = 'localhost'
ConnectDialog = ConnectDialog
LoginPrompt = False
Left = 344
Top = 32
end
object DataSource: TDataSource
DataSet = Query
Left = 440
Top = 32
end
object ConnectDialog: TMyConnectDialog
DatabaseLabel = 'Database'
PortLabel = 'Port'
SavePassword = True
Caption = 'Connect'
UsernameLabel = 'User Name'
PasswordLabel = 'Password'
ServerLabel = 'Server'
ConnectButton = 'Connect'
CancelButton = 'Cancel'
Left = 376
Top = 32
end
object Query: TMyQuery
SQLInsert.Strings = (
'INSERT INTO MYDAC_Text'
' (MYDAC_Text.Name, MYDAC_Text.TextField)'
'VALUES'
' (:Name, :TextField)')
SQLDelete.Strings = (
'DELETE FROM MYDAC_Text'
'WHERE'
' UID = :Old_UID')
SQLUpdate.Strings = (
'UPDATE MYDAC_Text'
'SET'
' Name = :Name, TextField = :TextField'
'WHERE'
' UID = :Old_UID')
SQLRefresh.Strings = (
'SELECT MYDAC_Text.Name, MYDAC_Text.TextField FROM MYDAC_Text'
'WHERE'
' MYDAC_Text.UID = :Old_UID')
Connection = MyConnection
SQL.Strings = (
'SELECT * FROM MYDAC_Text')
FetchAll = True
Left = 408
Top = 32
end
object OpenDialog: TOpenDialog
Left = 240
Top = 259
end
object SaveDialog: TSaveDialog
Left = 272
Top = 259
end
object sqCreateTable: TMyCommand
Connection = MyConnection
SQL.Strings = (
'CREATE TABLE MYDAC_Text ('
' UID INT NOT NULL AUTO_INCREMENT PRIMARY KEY,'
' Name VARCHAR(50),'
' TextField BLOB'
')')
Debug = True
Left = 344
Top = 68
end
object sqDropTable: TMyCommand
Connection = MyConnection
SQL.Strings = (
'DROP TABLE MYDAC_Text')
Debug = True
Left = 380
Top = 68
end
end
Demo源码：
Main.pas
unit Main;
interface
uses
{$IFNDEF LINUX}
Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
DBCtrls, ExtCtrls, Grids, DBGrids, StdCtrls, ToolWin, ComCtrls, MyDacVcl,
{$ELSE}
SysUtils, Types, Classes, QGraphics, QControls, QForms, QDialogs, QStdCtrls,
QDBCtrls, QComCtrls, QExtCtrls, QGrids, QDBGrids, MyDacClx,
{$ENDIF}
DBAccess, MyAccess, DB, MemDS;
type
TfmMain = class(TForm)
MyConnection: TMyConnection;
DBGrid: TDBGrid;
DataSource: TDataSource;
ToolBar: TPanel;
btOpen: TButton;
DBNavigator: TDBNavigator;
btClose: TButton;
ConnectDialog: TMyConnectDialog;
meComments: TDBMemo;
Query: TMyQuery;
Splitter1: TSplitter;
ToolBar1: TToolBar;
btLoad: TButton;
btSave: TButton;
OpenDialog: TOpenDialog;
SaveDialog: TSaveDialog;
ToolButton1: TToolButton;
btClear: TButton;
ToolButton2: TToolButton;
sqCreateTable: TMyCommand;
sqDropTable: TMyCommand;
btCreate: TButton;
btDrop: TButton;
procedure btOpenClick(Sender: TObject);
procedure btCloseClick(Sender: TObject);
procedure btLoadClick(Sender: TObject);
procedure btSaveClick(Sender: TObject);
procedure btClearClick(Sender: TObject);
procedure btCreateClick(Sender: TObject);
procedure btDropClick(Sender: TObject);
private
{ Private declarations }
public
{ Public declarations }
end;
var
fmMain: TfmMain;
implementation
{$R *.dfm}
procedure TfmMain.btOpenClick(Sender: TObject);
begin
Query.Open;
end;
procedure TfmMain.btCloseClick(Sender: TObject);
begin
Query.Close;
end;
procedure TfmMain.btLoadClick(Sender: TObject);
begin
if Query.Active and OpenDialog.Execute then begin
if Query.State = dsBrowse then
Query.Edit;
TBlobField(Query.FieldByName('TextField')).LoadFromFile(OpenDialog.FileName);
end;
end;
procedure TfmMain.btSaveClick(Sender: TObject);
begin
if not Query.EOF and SaveDialog.Execute then
TBlobField(Query.FieldByName('TextField')).SaveToFile(SaveDialog.FileName);
end;
procedure TfmMain.btClearClick(Sender: TObject);
begin
if Query.Active then begin
if Query.State = dsBrowse then
Query.Edit;
Query.FieldByName('TextField').Clear;
end;
end;
procedure TfmMain.btCreateClick(Sender: TObject);
begin
sqCreateTable.Execute;
end;
procedure TfmMain.btDropClick(Sender: TObject);
begin
sqDropTable.Execute;
end;
end.
很奇怪，我用MySQLFont写入的Longtext，读出没问题。
可是就是写入就Fail出那个内存溢出的错。
用UTF-8＋Unicode的选项。