本例效果图:
代码文件:
unit Unit1;interfaceuses Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms, Dialogs, StdCtrls, ExtCtrls, Grids, DBGrids, DB, ADODB;type TForm1 = class(TForm) DBGrid1: TDBGrid; DataSource1: TDataSource; ADODataSet1: TADODataSet; Panel1: TPanel; Button1: TButton; Button2: TButton; Button3: TButton; Button4: TButton; Button5: TButton; procedure FormCreate(Sender: TObject); procedure Button1Click(Sender: TObject); procedure Button2Click(Sender: TObject); procedure Button3Click(Sender: TObject); procedure Button4Click(Sender: TObject); procedure Button5Click(Sender: TObject); end;var Form1: TForm1;implementation{$R *.dfm}procedure TForm1.Button1Click(Sender: TObject);begin with ADODataSet1 do begin Close; CommandText := 'SELECT Continent, ' + 'AVG(Area) AS 平均面积, AVG(Population) AS 平均人口 ' + 'FROM country GROUP BY Continent'; Open; end;end;procedure TForm1.Button2Click(Sender: TObject);begin with ADODataSet1 do begin Close; CommandText := 'SELECT Continent, ' + 'SUM(Area) AS 面积总数, SUM(Population) AS 人口总数 ' + 'FROM country GROUP BY Continent'; Open; end;end;procedure TForm1.Button3Click(Sender: TObject);begin with ADODataSet1 do begin Close; CommandText := 'SELECT Continent, ' + 'MAX(Area) AS 面积最大, MIN(Population) AS 人口最少 ' + 'FROM country GROUP BY Continent'; Open; end;end;procedure TForm1.Button4Click(Sender: TObject);begin with ADODataSet1 do begin Close; CommandText := 'SELECT Continent, ' + 'MAX(Area + Population) AS 面积与人口总和最多, ' + 'MIN(Area + Population) AS 面积与人口总和最少 ' + 'FROM country GROUP BY Continent'; Open; end;end;procedure TForm1.Button5Click(Sender: TObject);begin with ADODataSet1 do begin Close; CommandText := 'SELECT COUNT(*) AS 记录总数 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. 窗体文件: object Form1: TForm1 Left = 0 Top = 0 Caption = 'Form1' ClientHeight = 407 ClientWidth = 626 Color = clBtnFace Font.Charset = DEFAULT_CHARSET Font.Color = clWindowText Font.Height = -11 Font.Name = 'Tahoma' Font.Style = [] OldCreateOrder = False OnCreate = FormCreate PixelsPerInch = 96 TextHeight = 13 object DBGrid1: TDBGrid Left = 0 Top = 33 Width = 626 Height = 374 Align = alClient DataSource = DataSource1 TabOrder = 0 TitleFont.Charset = DEFAULT_CHARSET TitleFont.Color = clWindowText TitleFont.Height = -11 TitleFont.Name = 'Tahoma' TitleFont.Style = [] end object Panel1: TPanel Left = 0 Top = 0 Width = 626 Height = 33 Align = alTop Caption = 'Panel1' TabOrder = 1 object Button1: TButton Left = 6 Top = 5 Width = 75 Height = 25 Caption = 'Button1' TabOrder = 0 OnClick = Button1Click end object Button2: TButton Left = 87 Top = 5 Width = 75 Height = 25 Caption = 'Button2' TabOrder = 1 OnClick = Button2Click end object Button3: TButton Left = 168 Top = 5 Width = 75 Height = 25 Caption = 'Button3' TabOrder = 2 OnClick = Button3Click end object Button4: TButton Left = 249 Top = 5 Width = 75 Height = 25 Caption = 'Button4' TabOrder = 3 OnClick = Button4Click end object Button5: TButton Left = 330 Top = 5 Width = 75 Height = 25 Caption = 'Button5' TabOrder = 4 OnClick = Button5Click end end object DataSource1: TDataSource DataSet = ADODataSet1 Left = 184 Top = 112 end object ADODataSet1: TADODataSet CursorType = ctStatic Parameters = <> Left = 232 Top = 184 endend