//选择 country 表中的 Name 字段SELECT Name FROM country//选择 country 表中的 Name、Area 和 Population 字段SELECT Name,Area,Population FROM country{多个字段时, 字段名是用 "," 隔开的}

unit Unit1;interfaceuses  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,  Dialogs, StdCtrls, ExtCtrls, Grids, DBGrids, DB, ADODB;type  TForm1 = class(TForm)    Panel1: TPanel;    Button1: TButton;    Button2: TButton;    DBGrid1: TDBGrid;    DataSource1: TDataSource;    ADODataSet1: TADODataSet;    procedure FormCreate(Sender: TObject);    procedure Button1Click(Sender: TObject);    procedure Button2Click(Sender: TObject);  end;var  Form1: TForm1;implementation{$R *.dfm}procedure TForm1.Button1Click(Sender: TObject);begin  with ADODataSet1 do begin    Close;    CommandText := 'SELECT Name FROM country';    Open;  end;end;procedure TForm1.Button2Click(Sender: TObject);begin  with ADODataSet1 do begin    Close;    CommandText := 'SELECT Name,Area,Population FROM country';    Open;  end;end;procedure TForm1.FormCreate(Sender: TObject);var  mdbFile: string;begin  mdbFile := GetEnvironmentVariable('COMMONPROGRAMFILES');  mdbFile := mdbFile + '\CodeGear Shared\Data\dbdemos.mdb';  ADODataSet1.ConnectionString := 'Provider=Microsoft.Jet.OLEDB.4.0;Data Source=' +    mdbFile + ';Persist Security Info=False';  DBGrid1.DataSource := DataSource1;  DataSource1.DataSet := ADODataSet1;end;end.