zoukankan      html  css  js  c++  java
  • 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.
    
  • 相关阅读:
    pytorch_基于cifar创建自己的数据集并训练
    Pytorch_3.8_多层感知机
    Pytorch_3.6_ SOFTMAX回归的从零实现
    Linux(debian)下的Python程序守护进程
    Ubuntu16.04安装OpenCV3.4.3
    Beaglebone black 安装docker
    电脑与虚拟机ping
    Beaglebone升级Python3.7过程
    多图上传预览
    放大镜代码
  • 原文地址:https://www.cnblogs.com/del/p/1491207.html
Copyright © 2011-2022 走看看