TClientDataSet[13]: 过滤

方法有:
1、Filter、Filtered
2、OnFilterRecord
3、SetRange、ApplyRange 或 SetRangeStart、SetRangeEnd、ApplyRange
(Range 相关还有: CancelRange、EditRangeStart、EditRangeEnd、KeyExclusive、Ranged)

下面三个例子测试前都要: 先在窗体上放置 ClientDataSet1、DataSource1、DBGrid1 并关联.

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Filter 测试:

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{ 准备测试数据 }
procedure TForm1.FormCreate(Sender: TObject);
begin
  with ClientDataSet1 do begin
    FieldDefs.Add('ID', ftInteger);
    FieldDefs.Add('Name', ftString, 6);
    FieldDefs.Add('Age', ftWord);
    CreateDataSet;
    AppendRecord([1, 'A',    11]);
    AppendRecord([2, 'AB',   22]);
    AppendRecord([3, 'ABC',  33]);
    AppendRecord([4, 'ABCD', 44]);
    AppendRecord([5, 'a',    55]);
    AppendRecord([6, 'ab',   66]);
    AppendRecord([7, 'abc',  77]);
    AppendRecord([8, 'abcd', 88]);
    AppendRecord([9, 'abcde']);
  end;
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
  ClientDataSet1.Filter := 'Name = ' + QuotedStr('ab');
  ClientDataSet1.Filtered := True;
end;

procedure TForm1.Button2Click(Sender: TObject);
begin
  ClientDataSet1.Filter := 'Name = ''ab''';
  ClientDataSet1.FilterOptions := [foCaseInsensitive];
  ClientDataSet1.Filtered := True;
end;

procedure TForm1.Button3Click(Sender: TObject);
begin
  ClientDataSet1.Filter := 'Name = ''a*''';
//  ClientDataSet1.FilterOptions := [foNoPartialCompare]; { 此选项使 * 功能无效 }
  ClientDataSet1.Filtered := True;
end;

procedure TForm1.Button4Click(Sender: TObject);
begin
  ClientDataSet1.Filter := 'Name Like ''ab%''';
  ClientDataSet1.Filtered := True;
end;

procedure TForm1.Button5Click(Sender: TObject);
begin
  ClientDataSet1.Filter := 'Name Like ''%c%''';
  ClientDataSet1.FilterOptions := [foCaseInsensitive];
  ClientDataSet1.Filtered := True;
end;

procedure TForm1.Button6Click(Sender: TObject);
begin
  ClientDataSet1.Filter := 'ID>2 and Age<77';
  ClientDataSet1.Filtered := True;
end;

procedure TForm1.Button7Click(Sender: TObject);
begin
  ClientDataSet1.Filter := 'not(ID>2 and Age<77)';
  ClientDataSet1.Filtered := True;
end;

procedure TForm1.Button8Click(Sender: TObject);
begin
  ClientDataSet1.Filter := 'ID<=1 or Age>=88';
  ClientDataSet1.Filtered := True;
end;

procedure TForm1.Button9Click(Sender: TObject);
begin
  ClientDataSet1.Filter := 'ID<>1 and ID<>3 and ID<>5 and ID<>7';
  ClientDataSet1.Filtered := True;
end;

procedure TForm1.Button10Click(Sender: TObject);
begin
  ClientDataSet1.Filter := 'Age - ID = 20';
  ClientDataSet1.Filtered := True;
end;

procedure TForm1.Button11Click(Sender: TObject);
begin
  ClientDataSet1.Filter := 'Age + ID > 60';
  ClientDataSet1.Filtered := True;
end;

procedure TForm1.Button12Click(Sender: TObject);
begin
  ClientDataSet1.Filter := 'Age * 2 = 22';
  ClientDataSet1.Filtered := True;
end;

procedure TForm1.Button13Click(Sender: TObject);
begin
  ClientDataSet1.Filter := 'Age / 2 = 22';
  ClientDataSet1.Filtered := True;
end;

procedure TForm1.Button14Click(Sender: TObject);
begin
  ClientDataSet1.Filter := 'Age<55 and Name Like ''AB%''';
  ClientDataSet1.Filtered := True;
end;

procedure TForm1.Button15Click(Sender: TObject);
begin
  ClientDataSet1.Filter := 'Age = Null'; { 其中的 Null 大小写均可 }
  ClientDataSet1.Filtered := True;
end;

procedure TForm1.Button16Click(Sender: TObject);
begin
  ClientDataSet1.Filter := 'ID>6 and Age<>null';
  ClientDataSet1.Filtered := True;
end;

SetRange 等测试:

---

{ 准备测试数据 }
procedure TForm1.FormCreate(Sender: TObject);
begin
  with ClientDataSet1 do begin
    FieldDefs.Add('ID', ftInteger);
    FieldDefs.Add('Name', ftString, 6);
    FieldDefs.Add('Age', ftWord);
    CreateDataSet;
    AppendRecord([1, 'A',    11]);
    AppendRecord([2, 'AB',   22]);
    AppendRecord([3, 'ABC',  33]);
    AppendRecord([4, 'ABCD', 44]);
    AppendRecord([5, 'a',    55]);
    AppendRecord([6, 'ab',   66]);
    AppendRecord([7, 'abc',  77]);
    AppendRecord([8, 'abcd', 88]);
  end;
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
  ClientDataSet1.IndexFieldNames := 'ID';

  ClientDataSet1.SetRangeStart;
  ClientDataSet1.FieldValues['ID'] := 3;
//  ClientDataSet1.KeyExclusive := True; { 排除边界值; 此值默认是 False, 也就是包含指定的边界 }

  ClientDataSet1.SetRangeEnd;
  ClientDataSet1.FieldValues['ID'] := 7;
//  ClientDataSet1.KeyExclusive := True; { 排除边界值 }

  ClientDataSet1.ApplyRange;
end;

procedure TForm1.Button2Click(Sender: TObject);
begin
  ClientDataSet1.IndexFieldNames := 'ID';

  ClientDataSet1.SetRange([2], [5]);
  ClientDataSet1.ApplyRange;
end;

procedure TForm1.Button3Click(Sender: TObject);
begin
  ClientDataSet1.IndexFieldNames := 'Age; Name';

  ClientDataSet1.SetRange([33, 'ABC'], [66, 'abc']);
  ClientDataSet1.ApplyRange;
end;

procedure TForm1.Button4Click(Sender: TObject);
begin
  ClientDataSet1.IndexFieldNames := 'Age; Name';

  ClientDataSet1.SetRange([33, 'ABC'], [66, 'abc']);

  ClientDataSet1.EditRangeStart;
  ClientDataSet1.KeyExclusive := True;

  ClientDataSet1.EditRangeEnd;
  ClientDataSet1.KeyExclusive := True;

  ClientDataSet1.ApplyRange;
end;

OnFilterRecord 测试:

---

{ 准备测试数据 }
procedure TForm1.FormCreate(Sender: TObject);
begin
  with ClientDataSet1 do begin
    FieldDefs.Add('ID', ftInteger);
    FieldDefs.Add('Name', ftString, 6);
    FieldDefs.Add('Age', ftWord);
    CreateDataSet;
    AppendRecord([1, 'A',    11]);
    AppendRecord([2, 'AB',   22]);
    AppendRecord([3, 'ABC',  33]);
    AppendRecord([4, 'ABCD', 44]);
    AppendRecord([5, 'a',    55]);
    AppendRecord([6, 'ab',   66]);
    AppendRecord([7, 'abc',  77]);
    AppendRecord([8, 'abcd', 88]);
  end;
  ClientDataSet1.Filtered := True; { 激活 OnFilterRecord 事件 }
end;

procedure TForm1.ClientDataSet1FilterRecord(DataSet: TDataSet; var Accept: Boolean);
begin
  if DataSet.FieldValues['ID'] mod 2 = 0 then
    Accept := True
  else
    Accept := False;
end;

补充: _ 在使用 like 时课代表单个字符.

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