学习 SQL 语句 - Select(8): 分组条件

代码文件:

---

//分组条件可以是 Where

procedure 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 Having

procedure TForm1.Button2Click(Sender: TObject);

begin

  with ADODataSet1 do begin

    Close;

    CommandText := 'SELECT Continent, AVG(Area) AS 平均面积 ' +

                   'FROM country GROUP BY Continent HAVING Continent<>"South America"';

    Open;

  end;

end;