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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; ADOConnection1: TADOConnection; ADODataSet1: TADODataSet; ADOCommand1: TAD 阅读全文
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//只要前五条记录procedure TForm1.Button1Click(Sender: TObject);begin with ADODataSet1 do begin Close; CommandText := 'SELECT TOP 5 * FROM country'; Open; end;end;//去除重复procedure TForm1.Button2Click(Sender: TObject);begin with ADODataSet1 do begin Close; CommandText := 'SELECT DISTINCTROW * FROM 阅读全文
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代码文件: //分组条件可以是 Whereprocedure TForm1.Button1Click(Sender: TObject);begin with ADODataSet1 do begin Close; CommandText := 'SELECT Continent, AVG(Area) AS 平均面积 ' + 'FROM country WHERE Continent="South America" GROUP BY Continent'; Open; end;end;//也可以是 Havingprocedure TForm1. 阅读全文
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Group By本来 Group By 也可以根据多个字段分组("," 隔开), 但这个例子只有 Continent 字段适合分组, 也只有 Area、Population 字段适合统计. 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) 阅读全文
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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; p 阅读全文
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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; B 阅读全文
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Order By Asc|Desc 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; B 阅读全文
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Where 用来指定查询条件;Like 和 Not Like 来指定模糊条件;模糊条件中:_ 表示任一字符;% 表示任一字符串;[] 表示一个集合. 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: 阅读全文
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//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;interfaceuses Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms, Dialogs, StdCtrls, ExtCtr 阅读全文
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//选择 country 表中的所有字段SELECT * FROM country{虽然 SQL 并不区分大小写, 但应习惯把关键字大写}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) Panel1: TPanel; Button1: TButton; Bu 阅读全文