应用TADOConnection、TADODataSet和TADOCommand组件

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本文介绍使用 ADO (ActiveX Data Objects) 进行数据库操作的方法，包括执行 SQL 查询、更新数据等常见操作。通过两个具体示例展示了如何在 Delphi 或 C++Builder 中利用 ADOQuery 和 ADOCommand 组件实现数据检索与交互。

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unit U_AdoQuery;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls, DB, ADODB, Buttons, DBClient, ExtCtrls,SQLEdit, Grids,
  DBGrids;

type
  TForm1 = class(TForm)
    DataSource1: TDataSource;
    QueryButton: TButton;
    EditCommandText: TSpeedButton;
    ADOQuery1: TADOQuery;
    SQLText: TMemo;
    Connection: TADOConnection;
    DBGrid1: TDBGrid;
    Label1: TLabel;
    procedure QueryButtonClick(Sender: TObject);
    procedure EditCommandTextClick(Sender: TObject);

  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

procedure TForm1.QueryButtonClick(Sender: TObject);
begin
  AdoQuery1.Close;
  AdoQuery1.SQL.Clear;
  AdoQuery1.SQL.Add(SQLText.Text);
  AdoQuery1.Open;
end;

procedure TForm1.EditCommandTextClick(Sender: TObject);
var
  Command: string;
begin
  Command := SQLText.Text;
  if EditSQL(Command, Connection.GetTableNames, Connection.GetFieldNames) then
      SQLText.Text := Command;
end;

end.

unit U_AdoCommand;
interface
uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls, DB, ADODB, Grids, DBGrids;

type
  TF_AdoCommand = class(TForm)
    ADOConnection1: TADOConnection;
    ADOCommand1: TADOCommand;
    DataSource1: TDataSource;
    DBGrid1: TDBGrid;
    ADODataSet1: TADODataSet;
    ADOCommand2: TADOCommand;
    ExcuteButton: TButton;
    CancelButton: TButton;
    DataSource2: TDataSource;
    DBGrid2: TDBGrid;
    CancelAllButton: TButton;
    ADODataSet2: TADODataSet;
    ExcuteAllButton: TButton;
    ComboBox1: TComboBox;
    Label1: TLabel;
    procedure ExcuteButtonClick(Sender: TObject);
    procedure CancelButtonClick(Sender: TObject);
    procedure CancelAllButtonClick(Sender: TObject);
    procedure ExcuteAllButtonClick(Sender: TObject);
    procedure FormCreate(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  F_AdoCommand: TF_AdoCommand;

implementation

{$R *.dfm}

procedure TF_AdoCommand.ExcuteButtonClick(Sender: TObject);
begin
if Combobox1.ItemIndex =0 then
//调用第一个ADO命令组件的Excute方法，并在DBGrid1中显示查询结果
  with ADOCommand1 do
  begin
      CommandType := cmdText;
      CommandText :='select *  from  country';
      ADODataSet1.Recordset := Execute;
  end
else
//调用第二个ADO命令组件的Excute方法，并在DBGrid2中显示查询结果
  with ADOCommand2 do begin
    CommandType := cmdText;
    CommandText :='select *  from  employee';
    ADODataSet2.Recordset := Execute;
  end;
end;

procedure TF_AdoCommand.CancelButtonClick(Sender: TObject);
begin
  if Combobox1.ItemIndex =0 then
   begin
     ADOCommand1.Cancel;
     ADODataSet1.Recordset :=nil ;
   end
  else
   begin
     ADOCommand2.Cancel;
     ADODataSet2.Recordset :=nil;
   end;
end;

procedure TF_AdoCommand.CancelAllButtonClick(Sender: TObject);
begin
   ADOCommand1.Cancel;
   ADOCommand2.Cancel;
   ADODataSet1.Recordset :=nil;
   ADODataSet2.Recordset :=nil;
end;

procedure TF_AdoCommand.ExcuteAllButtonClick(Sender: TObject);
var
i: Integer;
begin
  ADOCommand2.CommandText :='Update';
  for i := 0 to (ADOConnection1.CommandCount-1)  do
      begin
         if i=0 then
             begin
               ADOConnection1.Commands[i].CommandType := cmdText;
               ADOConnection1.Commands[i].CommandText :='select *  from  country';
                ADODataSet1.Recordset := ADOConnection1.Commands[i].Execute;
             end
         else  if i=1 then
              begin
               ADOConnection1.Commands[i].CommandType := cmdText;
               ADOConnection1.Commands[i].CommandText :='select *  from  employee';
               ADODataSet2.Recordset := ADOConnection1.Commands[i].Execute;

             end;
      end;
end;

procedure TF_AdoCommand.FormCreate(Sender: TObject);
var
i: Integer;
begin
  ComboBox1.Items.Clear;
  //添加的列表项的数目等于ADOConnection1组件所相关的TADOCommand组件的个数
  for i := 0 to (ADOConnection1.CommandCount-1)  do
     //添加的列表项为相关TADOCommand组件的名称
    Combobox1.Items.Add(ADOConnection1.Commands[i].Name) ;
  Combobox1.ItemIndex :=0;
end;

end.