MS Access

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This page explains how to use a Microsoft Access database using ODBC and FPC's built-in SQLDB.


MS Access specifics

UsePrimaryKeyAsKey

In the TSQLQuery properties, you may need to set Set UsePrimaryKeyAsKey: False

Get just-inserted autonumber primary key

After inserting data, Access 2000 and higher supports getting the just-inserted autonumber primary key using this query: 

SELECT @@IDENTITY

ODBC drivers

Windows

There are 2 different ODBC drivers for Microsoft Access:

  • the old driver that can only use .mdb format files, driver name is "Microsoft Access Driver (*.mdb)". Included in many Windows versions (since Windows 2000 up to and including Vista?); downloadable for older Windows versions as part of the MDAC components or Jet components. 32 bit only.
  • the new driver that can access both .mdb and .accdb files, driver name is "Microsoft Access Driver (*.mdb, *.accdb)". Downloadable as the "Microsoft Access Database Engine 2010 Redistributable"; available as 32 and 64 bit.

As usual, when using 32 bit Lazarus/FPC, use 32 bit ODBC drivers. When using 64 bit Lazarus/FPC, use 64 bit ODBC drivers.

Unix/Linux

The mdbtools project offers limited support for MS Accesss. It includes an ODBC driver which might be used. Try installing packages like mdbtools mdbtools-dev mdbtools-gmdb

At least on Debian, the ODBC driver name is "MDBTools".

Wildcards in SQL queries

Microsoft Access has a different wildcard syntax in SQL queries than other database systems. The following information is taken from a document "Intermediate Microsoft Jet SQL for Access 2000" at MSDN, but is no longer found at this place (some copies still exist in the web at third-party sites). Tested to be valid.

Wildcard Character Description
% (percent sign) Matches any number of characters and can be used anywhere in the pattern string.
_ (underscore) Matches any single character and can be used anywhere in the pattern string.
[] (square brackets) Matches any single character within the list that is enclosed within brackets, and can be used anywhere in the pattern string.
! (exclamation point) Matches any single character not in the list that is enclosed within the square brackets.
- (hyphen) Matches any one of a range of characters that is enclosed within the square brackets.

Note that

  • the WHERE condition in Access must be put in round parenthesis
  • strings must be single-quoted
  • dates must be formatted like #yyyy-mm-dd# (in year-month-day order and enclosed by '#')
  • field and table names with normally forbidden characters must be enclosed in square brackets.

Example: SELECT * FROM [Birthday Table] WHERE ([Birth date] >= #2000-01-01#)

File-based DSN Instructions

A file DSN is simply where the connection settings are written to a file. The reason for having a file DSN is if you want to distribute a data source connection to multiple users on different systems without having to configure a DSN for each system. For instance, I can create a file DSN to a reporting database on my desktop. I can then send the file to my users. My users can save the file DSN to their hard drives and then point their reporting applications at the file DSN.

If you want to use a file-based DSN with the SQLDB ODBC driver:

Set up the File DSN

  • Go to your [Data sources (ODBC)] at the control panel administrative tools.
  • Go to [File DSN] tab menu, Click Add, then Select <microsoft access driver>.
  • Next, browse to your current Lazarus project path to save your .DSN file, because that dsn file will contain the configuration needed to access your database file (.mdb).
  • Click Next, then Finish (you now have created a new .dsn file) of which will be use in your TODBCConnection [FileDSN].

File DSN contents

For reference, a file DSN that refers to an MS Access database may look something like this: 

[ODBC]
DRIVER=Microsoft Access Driver (*.mdb)
UID=admin
UserCommitSync=Yes
Threads=3
SafeTransactions=0
PageTimeout=5
MaxScanRows=8
MaxBufferSize=2048
FIL=MS Access
DriverId=25
DefaultDir=
DBQ=YOUR_msaccess.mdb

Configure your project to use file-based DSN

Usage of grids and other data bound controls is the same as for any other SQLDB connector, so that is not covered here.

As you're using an ODBC connection, you should have a TODBCConnection object.

TOBDCConnection Properties:

FileDSN: the path+filename to the DSN file saved earlier, e.g. c:\mylazarus\project1\myFile.dsn Username: admin (or whatever username you need if you are using Access security) this parameter may not be needed if no MS Access security is used Do not put any other entries in the properties.


System/User DSN

As explained in the ODBC article, you can also use system or user DSNs, where connection settings are defined in the ODBC control panel instead of stored in a file.

The TODBCConnection should have DatabaseName: <name_of_your_DSN>

DSN-less connection

As explained in the ODBC article, you can also create a DSN-less connection to your Access database where you can specify all connection parameters in code, something like: 

  //Notice we're using the new MS Access driver, we could probably use the old one too:
  conn.Driver:='Microsoft Access Driver (*.mdb, *.accdb)';
  conn.Params.Add('DBQ=c:\somedirectory\test.mdb');
  ... add whatever parameters you want/need...

Here is an example how to query a table in an Access mdb file using TODBCConnection, TSQLTransaction and TSQLQuery; the mdb file exists in the same folder as the project binary: 

procedure TForm1.Button1Click(Sender: TObject);
begin
  //connection
  ODBCConnection1.Driver := 'Microsoft Access Driver (*.mdb, *.accdb)';
  ODBCConnection1.Params.Add('DBQ='+Application.Location+'test.mdb');      // path to mdb file required
  ODBCConnection1.Params.Add('Locale Identifier=1031');
  ODBCConnection1.Params.Add('ExtendedAnsiSQL=1');
  ODBCConnection1.Params.Add('CHARSET=ansi');
  ODBCConnection1.Connected := True;
  ODBCConnection1.KeepConnection := True;
     
  //transaction
  SQLTransaction1.DataBase := ODBCConnection1;
  SQLTransaction1.Action := caCommit;
  SQLTransaction1.Active := True;
     
  SQLQuery1.DataBase := ODBCConnection1;
  SQLQuery1.UsePrimaryKeyAsKey := False;
  SQLQuery1.SQL.Text := 'select * from Customers';
  SQLQuery1.Open;
end;

Example code

Lazarus: data bound controls on forms

Working Source code sample:(Updated2_with_add_delete_update) http://www.mediafire.com/file/ne1jx3zpnwzefq3/msaccesstest2.zip [Dead link - November 2020] 

unit Unit1; 

{$mode objfpc}{$H+}

interface

uses
  Classes, SysUtils, odbcconn, sqldb, db, FileUtil, LResources, Forms, Controls,
  Graphics, Dialogs, DBGrids, DbCtrls, StdCtrls, Printers, PrintersDlgs;

type

  { TForm1 }

  TForm1 = class(TForm)
    Button1: TButton;
    Button2: TButton;
    Button3: TButton;
    Button4: TButton;
    Datasource1: TDatasource;
    DBEdit1: TDBEdit;
    DBEdit2: TDBEdit;
    DBGrid1: TDBGrid;
    ODBCConnection1: TODBCConnection;
    PrintDialog1: TPrintDialog;
    SQLQuery1: TSQLQuery;
    SQLTransaction1: TSQLTransaction;
    procedure Button1Click(Sender: TObject);
    procedure Button2Click(Sender: TObject);
    procedure Button3Click(Sender: TObject);
    procedure Button4Click(Sender: TObject);
    procedure FormCloseQuery(Sender: TObject; var CanClose: boolean);
    procedure FormShow(Sender: TObject);
  private
    { private declarations }
    procedure PrintDbGrid(dbGrid:TdbGrid);
  public
    { public declarations }
  end; 

var
  Form1: TForm1; 

implementation

{ TForm1 }

procedure TForm1.FormShow(Sender: TObject);
begin
  //connection
  ODBCConnection1.FileDSN := ExtractFilePath(Application.ExeName) + 'file.dsn';
  ODBCConnection1.Connected := True;
  ODBCConnection1.KeepConnection := True;

  //transaction
  SQLTransaction1.DataBase := ODBCConnection1;
  SQLTransaction1.Action := caCommit;
  SQLTransaction1.Active := True; //not applied to ms access(false)

  SQLQuery1.DataBase := ODBCConnection1;
  SQLQuery1.UsePrimaryKeyAsKey := False;

  SQLQuery1.SQL.Text := 'select * from table1';

  // :id is the parameter for the field name id
  SQLQuery1.deleteSQL.Text := 'delete from table1 where id=:id';
  //:name is the parameter for the field name name
  SQLQuery1.updateSQL.Text := 'update table1 set name=:name where id=:id';

  DataSource1.DataSet := SQLQuery1;
  DBGrid1.DataSource := DataSource1;
  DBGrid1.ReadOnly := true;

  DBEdit1.DataField := 'id';
  DBEdit1.DataSource := DataSource1;
  DBEdit2.DataField := 'name';
  DBEdit2.DataSource := DataSource1;

  SQLQuery1.Open;
end;

function MulDiv(nNumber, nNumerator, nDenominator: Integer): Integer;
begin
  Result:=Round(int64(nNumber)*int64(nNumerator)/nDenominator);
end;
procedure TForm1.PrintDbGrid(dbGrid:TdbGrid);
const
  LeftMargin = 0.05;
  TopMargin = 0.05;
  BottomMargin = 0.05;
var
  i: integer;
  x,y: integer;
begin
  if PrintDialog1.Execute then
    begin
    Printer.BeginDoc;
    Printer.Canvas.Font.Size := 12;

    y := Round(TopMargin*Printer.PageHeight);
    dbGrid.DataSource.DataSet.First;
    while not dbGrid.DataSource.DataSet.Eof do
      begin
      x := Round(LeftMargin*Printer.PageWidth);
      for i := 0 to dbGrid.DataSource.DataSet.FieldCount-1 do
        begin
        printer.Canvas.TextOut(x,y,dbGrid.DataSource.DataSet.Fields[i].AsString);
        x := x + MulDiv(dbGrid.Columns[i].Width,72, dbGrid.Width);
        end;
      dbGrid.DataSource.DataSet.Next;
      y := y + printer.Canvas.TextHeight('A');
      if y > (1-TopMargin-BottomMargin)* Printer.PageHeight then
        begin
        y := Round(TopMargin*Printer.PageHeight);
        Printer.NewPage;
        end;
      end;
    Printer.EndDoc;
    end
    else
    Form1.caption := 'NO PRINTER INSTALLED';
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
  PrintDbGrid(DBGrid1);
end;

procedure TForm1.Button2Click(Sender: TObject);
begin
if button2.Caption = 'new' then
begin
  SQLQuery1.Insert;
  button2.Caption := 'save';
  exit
  end
  else
  begin
    if (dbedit1.Text = '') or (dbedit2.Text = '')
    then
    begin
    SQLQuery1.Cancel;
    end
    else
    begin
    if SQLQuery1.State = dsInsert then
       begin
       SQLQuery1.Post;
       SQLQuery1.ApplyUpdates;
       Form1.caption := 'ADDED';
       end;
    end;
  end;
button2.Caption := 'new';
end;

procedure TForm1.Button3Click(Sender: TObject);
begin
if SQLQuery1.RecordCount>0 then
  begin
  SQLQuery1.Delete;
  SQLQuery1.ApplyUpdates;

  //REMOVED or ADD this 2 lines if there is a problem in your SQLdB
  //THESE 2 lines apparently work around a bug in SQLdB for MS_Access dataBase'
  //**** missing reference to bugtracker item; please create a bugtracker item
  //SQLQuery1.Close;
  //SQLQuery1.Open;


  Form1.caption := 'DELETED';
  end;
end;

procedure TForm1.Button4Click(Sender: TObject);
begin
  if SQLQuery1.RecordCount>0 then
  begin
    SQLQuery1.Edit;
    SQLQuery1.Post;
    Sqlquery1.ApplyUpdates;
    Form1.caption := 'UPDATED';
  end;
end;

procedure TForm1.FormCloseQuery(Sender: TObject; var CanClose: boolean);
begin
  SQLQuery1.Close;
  CanClose := True;
end;

initialization
  {$I unit1.lrs}

end.

Create a database programmatically

Using either ODBC driver, you can programmatically create Microsoft Access databases. The following code is valid for both 32-bit and 64-bit applications on Windows.

Example code: 

uses
  ..., sysutils, odbcsqldyn;

const
   ODBC_ADD_DSN=1;
   { just for reference...
   ODBC_CONFIG_DSN=2;
   ODBC_REMOVE_DSN=3;
   ODBC_ADD_SYS_DSN=4;
   ODBC_CONFIG_SYS_DSN=5;
   ODBC_REMOVE_SYS_DSN=6;
   ODBC_REMOVE_DEFAULT_DSN=7; }

function SQLConfigDataSource(hwndParent: Integer; fRequest: Integer;
  lpszDriverString: PChar; lpszAttributes: PChar): Integer; stdcall;
  external 'odbccp32.dll';

function SQLInstallerError(iError: integer; pfErrorCode: PInteger;
  lpszErrorMsg: String; cbErrorMsgMax: integer; pcbErrorMsg: PInteger): integer; stdcall;
  external 'odbccp32.dll';

procedure CreateAccessDatabase(DatabaseFile: string);
var
  cmd: String;
  driver: String;
  errCode, errMsgLength: DWord;
  errMsg: String;
  retCode: integer;
  ext: String;
begin
  ext := Lowercase(ExtractFileExt(DatabaseFile));

  driver := 'Microsoft Access Driver (*.mdb, *.accdb)';
  { With this driver,
    CREATE_DBV12 will create an .accdb format database;
    CREATE_DBV4 will create an .mdb format database
    http://stackoverflow.com/questions/9205633/how-do-i-specify-the-odbc-access-driver-format-when-creating-the-database
  }
  if ext = '.mdb' then
    cmd := 'CREATE_DBV4="' + DatabaseFile + '"'
  else if ext = '.accdb' then
    cmd := 'CREATE_DBV12="' + DatabaseFile + '"'
  else
    raise Exception.Create('Invalid database file extension.');

  retCode := SQLConfigDataSource(0, ODBC_ADD_DSN, PChar(driver), PChar(cmd));
  if not (retCode in [SQL_SUCCESS, SQL_SUCCESS_WITH_INFO]) then
  begin
    //try alternate driver
    driver := 'Microsoft Access Driver (*.mdb)';
    cmd := 'CREATE_DB="' + DatabaseFile + '"';
    retCode := SQLConfigDataSource(0, ODBC_ADD_DSN, PChar(driver), PChar(cmd));
  end;

  if not (retCode in [SQL_SUCCESS, SQL_SUCCESS_WITH_INFO]) then
  begin
    errCode := 0;
    errMsgLength := 0;
    SetLength(errMsg, SQL_MAX_MESSAGE_LENGTH);
    SQLInstallerError(1, @errCode, PChar(errMsg), Length(errMsg), @errMsgLength);
    SetLength(errMsg, errMsgLength);
    raise Exception.CreateFmt('Error creating Access database: %s', [errMsg]);
  end;
end;

Character set issues

Old Access databases are encoded using an ANSI character set (I don't know about new ones - they probably use wide strings). Therefore, non-ASCII characters are not displayed correctly in a DBGrid or other data-aware controls. This can be fixed by attaching handlers to the OnGetText and OnSetText events of the dataset after opening: 

uses
  lconvencoding;
 
procedure TForm1.SQLQuery1AfterOpen(DataSet: TDataSet);
var
  i: Integer;  
begin
  for i:=0 to DataSet.Fields.Count-1 do
  begin
    if DataSet.Fields[i].DataType=ftString then
    begin
      DataSet.Fields[i].OnGetText := @ConvertFromDB;
      DataSet.Fields[i].OnSetText := @ConvertToDB;
    end;
  end;
end;
 
procedure TForm1.ConvertFromDB(Sender: TField; var aText: string; DisplayText: Boolean);
begin
  if not Sender.IsNull then
    aText := WinCPToUTF8(Sender.AsString);  // if encoded in windows default code page
end;
 
procedure TForm1.ConvertToDB(Sender: TField; const aText: string);
begin
  if aText <> '' then 
    Sender.Value := UTF8ToWinCP(aText);
end;

Example database

Microsoft Access ships with the Northwind example database.

If you only have the Access Runtime installed, you can use this alternative database from the Mondial project as a test database: [1] [Dead link - November 2020]

See also

  • ODBCConn The ODBC connector this article uses
Retrieved from "https://wiki.freepascal.org/index.php?title=MS_Access&oldid=159858"