Koneksi Database Dengan ADO

Halaman : 3
MAKE AN ADODB CONNECTION USING OLE-AUTOMATION

// ******************************************************************
// MAKE AN ADODB CONNECTION USING OLE-AUTOMATION
// Category : ADO
// ******************************************************************

{…}
uses
ComObj;
{…}

function OpenConnection(ConnectionString: AnsiString): integer;
var
ADODBConnection: OleVariant;
begin
ADODBConnection := CreateOleObject(’ADODB.Connection’);
ADODBConnection.CursorLocation := 3; // User client
ADODBConnection.ConnectionString := ConnectionString;
Result := 0;
try
ADODBConnection.Open;
except
Result := -1;
end;
end;

function DataBaseConnection_Test(bMessage: boolean): AnsiString;
var
asTimeout,
asUserName,
asPassword,
asDataSource,
ConnectionString: AnsiString;
iReturn: Integer;
OldCursor: TCursor;
begin
OldCursor := Screen.Cursor;
Screen.Cursor := crHourGlass;
asTimeout := ‘150′;
asUserName := ‘NT_Server’;
asPassword := ‘SA’;
asDataSource := ‘SQL Server - My DataBase’;

ConnectionString := ‘Data Source = ‘ + asDataSource +
‘User ID = ‘ + asUserName +
‘Password = ‘ + asPassword +
‘Mode = Read|Write;Connect Timeout = ‘ + asTimeout;
try
iReturn := OpenConnection(ConnectionString);

if (bMessage) then
begin
if (iReturn = 0) then
Application.MessageBox(’Connection OK!’, ‘Information’, MB_OK)
else if (iReturn = -1) then
Application.MessageBox(’Connection Error!’, ‘Error’, MB_ICONERROR + MB_OK);
end;

if (iReturn = 0) then
Result := ConnectionString
else if (iReturn = -1) then
Result := ”;
finally
Screen.Cursor := OldCursor;
end;
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
DataBaseConnection_Test(true);
end;

MS-SQL : CONNECTION IS IN USE BY ANOTHER STATEMENT

// ******************************************************************
// MS-SQL : CONNECTION IS IN USE BY ANOTHER STATEMENT
// Category : ADO
// ******************************************************************

{
When porting a larger database application (130k LOC) that worked fine with
Oracle and InterBase to MS-SQL (6.5), I frequently got the error message
‘connection is in use by another statement’.

At first, creating a new TDatabase for each TTable/ TQuery seemed to be
necessary.

Then I found what was ‘wrong’ (not really wrong.. :-)

To speed up some of my queries, I had set the property Unidirectional to true.
Delphi creates for such queries only one cursor (versus two for bidirectional
queries or TTables). After removing the assignments of Unidirectional := true
the error message disappeared and everything worked fine.

The following code resulted in the exception ‘connection is in use by another
statement’:
}

// dataBaseNameS : string is the name of the alias (MS-SQL 6.5)
begin
Query1 := TQuery.Create (Application);
With Query1 do
begin
DatabaseName := dataBaseNameS;
SQL.Text := ‘SELECT * FROM ABLESTOP’;
// the exception disappears if the following is removed
Unidirectional := True;
Open;
end;
ShowMessage (’ok’)

Table1 := TTable.Create (Self);
With Table1 do
begin
DatabaseName := dataBaseNameS;
TableName := ‘COMPONENT_PLAN’;
UpdateMode := upWhereKeyOnly;
Open
end;

Table1.Insert;
Table1.FieldByName (’PARTNO’).AsString := IntToStr (GetTickCount);
Table1.FieldByName (’ID’).AsString := ‘WWxx’;
Table1.FieldByName (’VERSION’).AsInteger := 1;
// the exception will occurr in the next statement:
// “Connection is in use by another statement”
Table1.Post;
end;

DETECT, WHICH VERSION OF ADO IS INSTALLED

// ******************************************************************
// DETECT, WHICH VERSION OF ADO IS INSTALLED
// Category : ADO
// ******************************************************************

{
With different versions of MDAC available it is sometimes useful to know that your a
application won’t fail because a user hasn’t got the latest version installed.
The following function returns the ADO version installed, you need to place ComObj in
the uses clause to use this function.
}

function GetADOVersion: Double;
var
ADO: Variant;
begin
try
ADO := CreateOLEObject(’adodb.connection’);
Result := StrToFloat(ADO.Version);
ADO := Null;
except
Result := 0.0;
end;
end;

// To use this function try something like:

procedure TForm1.Button1Click(Sender: TObject);
const
ADOVersionNeeded = 2.5;
begin
if GetADOVersion
end;
<>

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