The greatest advantage of mysql versus mssql is that mysql is free!
Other advantages of mysql over mssql is that mysql can run on linux,
windows, mac os, novel etc
Don't get me wrong, MSSQL is very robust and offers a whole load of features
but where I come from (Kenya) its not every day that someone spends tens of
thousands of dollars for software; downsides of MSSQL is (for me at least)
1. is cost, 2. heavy protocol 3. (this is very personal) its not open by
nature. I prefer seeing the lines of code that run my systems (including the
database) which helps me optimize my software for the particular task.
I wont say one is better than the other; All I can say that depending on the
task at hand; one can be better than the other.
I've uploaded on the files section (3tier.rar) that is a very simple 3 tier
application; the client sends a command to the server then the server does
the database stuff and replies to the client; it returns which class every
student is in. note that the client doesn't do any SQL; that's done by the
application server. It uses Delphi and indy10 (ok its not really connecting
to a database; but if you read the source that's just a line of code . in
fact it can connect to virtually any back end)
It's a far cry from a perfect app; no error handling; no compression to
further make the protocol more smaller, no reconnection but it's a good
start. Whoops I cant upload files so here are the dumps of the files
<<< SERVER >>>
Unit1.dfm
object Form1: TForm1
Left = 192
Top = 135
Width = 696
Height = 480
Caption = 'Form1'
Color = clBtnFace
Font.Charset = DEFAULT_CHARSET
Font.Color = clWindowText
Font.Height = -11
Font.Name = 'MS Sans Serif'
Font.Style = []
OldCreateOrder = False
OnCreate = FormCreate
OnDestroy = FormDestroy
PixelsPerInch = 96
TextHeight = 13
object IdTCPServer1: TIdTCPServer
Bindings = <>
DefaultPort = 4566
OnExecute = IdTCPServer1Execute
Left = 72
Top = 80
end
end
Unit1.pas
unit Unit1;
interface
uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs, IdBaseComponent, IdComponent, IdTCPServer, IdContext,
idIOHandler;
type
TForm1 = class(TForm)
IdTCPServer1: TIdTCPServer;
procedure FormCreate(Sender: TObject);
procedure FormDestroy(Sender: TObject);
procedure IdTCPServer1Execute(AContext: TIdContext);
private
{ Private declarations }
procedure getname(IOHandler : TidIOHandler);
public
{ Public declarations }
end;
var
Form1: TForm1;
implementation
{$R *.dfm}
procedure TForm1.FormCreate(Sender: TObject);
begin
IdTCPServer1.Active:=True;
end;
procedure TForm1.FormDestroy(Sender: TObject);
begin
IdTCPServer1.Active:=false;
end;
procedure TForm1.getname(IOHandler: TidIOHandler);
var
I: Integer;
nme,res : string;
chr : char;
begin
//WARNING : THIS PROCEDURE IS THREDED - KEEP IT THREAD SAFE - CHRIS
// MANY CLIENTS CAN CALL THIS ATT THE SAME TIME WHEN MANY CLIENTS ARE
CONNECTED TO THIS SERVER
chr:=#1;
while chr<>#0 do
begin
chr:=IOHandler.ReadChar;
if chr<>#0 then
nme:=nme+chr;
end; // while
// we now have the name
// we can do whatever SQL we want here for example
// ADOQuery1.SQL.Text:='select class from mytable where name =
'+quotedstr(nme)
// ADOQUery1.open;
// res:=ADOQuery1.fieldbyname('class').asstring
// but for now - the easy way
res:='the class from the server!';
for I := 1 to length(res) do // Iterate
IOHandler.write(res[i]); // client waiting for the class; send it to
them
IOHandler.write(#0); // to show client thats the end of the class
// we are done!
end;
procedure TForm1.IdTCPServer1Execute(AContext: TIdContext);
begin
//WARNING : THIS PROCEDURE IS THREDED - KEEP IT THREAD SAFE - CHRIS
// MANY CLIENTS CAN CALL THIS ATT THE SAME TIME WHEN MANY CLIENTS ARE
CONNECTED TO THIS SERVER
with AContext.Connection.IOHandler do
begin
case ReadChar of //
'A' : getname(AContext.Connection.IOHandler); // aha! he wants a name
'B' : ; // do some other stuff;
'C' : ; // do even more stuff;
'D' : Application.Terminate // kill application server (for some
reason):
end; // case
end; // with
end;
end.
Project2.dpr
program Project2;
uses
Forms,
Unit1 in 'Unit1.pas' {Form1};
{$R *.res}
begin
Application.Initialize;
Application.CreateForm(TForm1, Form1);
Application.Run;
end.
<< CLIENT >>
Unit1.dfm
object Form1: TForm1
Left = 192
Top = 135
Width = 696
Height = 480
Caption = 'Form1'
Color = clBtnFace
Font.Charset = DEFAULT_CHARSET
Font.Color = clWindowText
Font.Height = -11
Font.Name = 'MS Sans Serif'
Font.Style = []
OldCreateOrder = False
OnCreate = FormCreate
OnDestroy = FormDestroy
PixelsPerInch = 96
TextHeight = 13
object Label1: TLabel
Left = 80
Top = 16
Width = 28
Height = 13
Caption = 'Name'
end
object Button1: TButton
Left = 80
Top = 72
Width = 75
Height = 25
Caption = 'Get Age'
TabOrder = 0
OnClick = Button1Click
end
object Edit1: TEdit
Left = 80
Top = 40
Width = 121
Height = 21
TabOrder = 1
end
object IdTCPClient1: TIdTCPClient
ConnectTimeout = 0
Host = '127.0.0.1'
IPVersion = Id_IPv4
Port = 4566
ReadTimeout = 0
Left = 192
Top = 80
end
end
unit1.pas
unit Unit1;
interface
uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs, IdBaseComponent, IdComponent, IdTCPConnection, IdTCPClient,
StdCtrls;
type
TForm1 = class(TForm)
Button1: TButton;
Edit1: TEdit;
Label1: TLabel;
IdTCPClient1: TIdTCPClient;
procedure Button1Click(Sender: TObject);
procedure FormCreate(Sender: TObject);
procedure FormDestroy(Sender: TObject);
private
{ Private declarations }
public
{ Public declarations }
end;
var
Form1: TForm1;
implementation
// Protocol is simple: if you want to get the class of a person send
A<name>#0
// the server will return <class>#0
{$R *.dfm}
procedure TForm1.Button1Click(Sender: TObject);
var
cls : string;
chr : char;
begin
cls:='';
IdTCPClient1.IOHandler.Write('A'+Edit1.Text+#0); // A = get AGE followed
by name then null to show end of name
chr:=#1;
while chr<>#0 do
begin
chr:=IdTCPClient1.IOHandler.ReadChar;
if chr<>#0 then
cls:=cls+chr;
end; // while
ShowMessage(cls);
end;
procedure TForm1.FormCreate(Sender: TObject);
begin
idtcpclient1.connect;
end;
procedure TForm1.FormDestroy(Sender: TObject);
begin
IdTCPClient1.Disconnect;
end;
end.
Project1.dpr
program Project1;
uses
Forms,
Unit1 in 'Unit1.pas' {Form1};
{$R *.res}
begin
Application.Initialize;
Application.CreateForm(TForm1, Form1);
Application.Run;
end.
PO Box 627 00502 Karen,
Nairobi, Kenya.
Mobile: +254 722 996532
Fixed: +254 20 2050859
[EMAIL PROTECTED]
_____
From: [email protected] [mailto:[EMAIL PROTECTED] On Behalf
Of Marselle
Sent: 01 May 2008 4:08 p
To: [email protected]
Subject: RE: [delphi-en] Mssql Locking causes Delphi App to crash
Chris.. I totally agree... perhaps you may want to send him a small example
here on how to set a nTier environment.. also is MySQL lic cost very
much...? you may want to add some pro's and cons about that as well
--- On Thu, 5/1/08, Chris <[EMAIL PROTECTED] <mailto:jangita%40jangita.com>
com> wrote:
From: Chris <[EMAIL PROTECTED] <mailto:jangita%40jangita.com> com>
Subject: RE: [delphi-en] Mssql Locking causes Delphi App to crash
To: [EMAIL PROTECTED] <mailto:delphi-en%40yahoogroups.com> ps.com
Date: Thursday, May 1, 2008, 7:58 AM
Hi,
I have been through the same thing; sadly to say the only way I solved it
was to change my database backend to mysql from mssql; My Delphi application
is currently running in 700 locations countrywide; so the database server is
hit with about 5 requests per second with over 14,000 simultaneous
connections and its all _smooth_.
Your case seems to be that you are connecting MSSQL clients via a wan
connection which I can guess is not as fast as a LAN connection; I don't
think the problem is the database backend or Delphi; its mysql. Not a
problem per-say; its just that MSSQL protocol over a network is "chatty" and
is quite heavy - not recommended to be used over the internet and other wan
networks where speed doesn't come easy.
You might find that the application is exceptionally slow and your ADO
connections are timing out over slow networks; I suggest you use a database
backend that is network friendly and has a very light protocol. Or build a 3
tier system where the clients run an application that communicate the bare
nessessities to an application server which translates into the commands
that will hit the database.
Hope this helps
PO Box 627 00502 Karen,
Nairobi, Kenya.
Mobile: +254 722 996532
Fixed: +254 20 2050859
[EMAIL PROTECTED] com
_____
From: [EMAIL PROTECTED] ps.com [mailto:[EMAIL PROTECTED] ps.com] On
Behalf
Of edsynergy
Sent: 30 April 2008 6:41 p
To: [EMAIL PROTECTED] ps.com
Subject: [delphi-en] Mssql Locking causes Delphi App to crash
I have just gone live with a delphi app which has mssql at the backend.
Under load testing it has been well behaved. It is now installed in a
large health organisation with users coming in over wan connections to
the sql server. For periods the system performs well and then it
crashes. All other users of the system also crash out as well. The
application will still launch and they can even log on but meaningful
work is not possible.
I have reviewed the code and cannot find an issue there. It would be
easy for me to blame the network/ old pc's ( and not doubt the clients
IT support could point a the software) but I rather get to the bottom
of it. The sql server is not on a dedicated server. It is one of
these new fangled virtual servers and I wonder if this is the issue.
After all it is only using the chunk of memory allocated to it by the
real server it is on. Would this impact on performance. Any views
would be much appreciated.
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