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  • 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:



    代码文件:
    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.
    
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  • 原文地址:https://www.cnblogs.com/del/p/1491207.html
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