unit1.~pas

Delphi数据库编程

unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, DB, DBTables, Grids, DBGrids, StdCtrls;

type
  TForm1 = class(TForm)
    DataSource1: TDataSource;
    Query1: TQuery;
    DBGrid1: TDBGrid;
    Button1: TButton;
    procedure Button1Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

procedure TForm1.Button1Click(Sender: TObject);
 begin
    Query1.close;
    Query1.DatabaseName :='ACCJIAOXUE';
    Query1.SQL.Clear ;
    Query1.SQL.Add('SELECT 学生表.姓名,AVG(成绩表.成绩) as 平均成绩');
    Query1.SQL.Add('From 学生表,成绩表');
    Query1.SQL.Add('where  学生表.学号=成绩表.学号');
    Query1.SQL.Add('Group by 学生表.姓名 ');
    Query1.SQL.Add('Order by  2');
    Query1.Open ;
end;

end.