TClientDataSet[11]: 分组统计

设计时实现的分组统计:

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运行时实现的分组统计:

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//前期只需要添加 ClientDataSet1、DataSource1、DBGrid1; 事件只需要关联窗体的 OnCreate



unit Unit1;



interface



uses

  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,

  Dialogs, Grids, DBGrids, DB, DBClient;



type

  TForm1 = class(TForm)

    DBGrid1: TDBGrid;

    DataSource1: TDataSource;

    ClientDataSet1: TClientDataSet;

    procedure FormCreate(Sender: TObject);

  private

    procedure OnGetText_Agg1(Sender: TField; var Text: string;

      DisplayText: Boolean);

    procedure OnGetText_Agg2(Sender: TField; var Text: string;

      DisplayText: Boolean);

  public

  end;



var

  Form1: TForm1;



implementation



{$R *.dfm}



procedure TForm1.FormCreate(Sender: TObject);

begin

  { 关联数据控件 }

  DBGrid1.DataSource := DataSource1;

  DataSource1.DataSet := ClientDataSet1;



  { 先打开前面例子中留下的测试文件 }

  ClientDataSet1.LoadFromFile('C:\Temp\Test.xml');



  { 添加索引, 其中分组级别是 2 }

  ClientDataSet1.AddIndex('Index1', '班级;年龄', [], '', '', 2);

  { 给数据集指定此索引 }

  ClientDataSet1.IndexName := 'Index1';



  { 数据结构变化时一般需要先关闭数据集 }

  ClientDataSet1.Close;



  { 添加统计字段 Agg1: 按班分组统计语文总成绩 }

  with TAggregateField.Create(Self) do begin

    FieldName := 'Agg1';

    Expression := 'Sum(语文成绩)';

    IndexName := 'Index1';

    GroupingLevel := 1;

    Active := True;

    OnGetText := OnGetText_Agg1;

    DataSet := ClientDataSet1;

  end;

  { 添加统计字段 Agg2: 各班分别按年龄分组统计语文总成绩 }

  with TAggregateField.Create(Self) do begin

    FieldName := 'Agg2';

    Expression := 'Sum(语文成绩)';

    IndexName := 'Index1';

    GroupingLevel := 2;

    Active := True;

    OnGetText := OnGetText_Agg2;

    DataSet := ClientDataSet1;

  end;



  { 需要在 DBGrid 中显示的字段 }

  with DBGrid1.Columns do begin

    Add.FieldName := '班级';

    Add.FieldName := '姓名';

    Add.FieldName := '年龄';

    Add.FieldName := '语文成绩';

    Add.FieldName := 'Agg1';

    Add.FieldName := 'Agg2';

  end;



  { 打开数据集并激活统计 }

  ClientDataSet1.Open;

  ClientDataSet1.AggregatesActive := True;

end;



procedure TForm1.OnGetText_Agg1(Sender: TField; var Text: string; DisplayText: Boolean);

begin

  if gbLast in ClientDataSet1.GetGroupState(1) then

    Text := Sender.AsString else Text := '';

end;



procedure TForm1.OnGetText_Agg2(Sender: TField; var Text: string; DisplayText: Boolean);

begin

  if gbLast in ClientDataSet1.GetGroupState(2) then

    Text := Sender.AsString else Text := '';

end;



end.