学习 SQL 语句 - Select(2): 指定表中的字段

//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}


 
   

本例效果图:

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代码文件:

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unit Unit1;



interface



uses

  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.