FireDAC 下的 Sqlite [9] - 关于排序

发布时间：2020-12-12 23:51:50 所属栏目：百科来源：网络整理

导读：SQLite 内部是按二进制排序,可以支持 ANSI; FrieDAC 通过 TFDSQLiteCollation 支持了 Unicode 排序,并可通过其 OnCompare 事件自定义排序. 下面的例子,测试了这两种排序的不同. 可把下面代码直接贴在空白窗体上,以快速完成窗体设计: object DBGrid1: TDBGrid

SQLite 内部是按二进制排序,可以支持 ANSI; FrieDAC 通过 TFDSQLiteCollation 支持了 Unicode 排序,并可通过其 OnCompare 事件自定义排序.

下面的例子,测试了这两种排序的不同.

可把下面代码直接贴在空白窗体上,以快速完成窗体设计:
object DBGrid1: TDBGrid Left = 0 Top = 0 Width = 297 Height = 199 Align = alLeft DataSource = DataSource1 TabOrder = 0 TitleFont.Charset = DEFAULT_CHARSET TitleFont.Color = clWindowText TitleFont.Height = -11 TitleFont.Name = 'Tahoma' TitleFont.Style = [] end object Button1: TButton Left = 303 Top = 24 Width = 110 Height = 25 Caption = 'SQLite '#20869#32622#25490#24207 TabOrder = 1 OnClick = Button1Click end object Button2: TButton Left = 303 Top = 65 Width = 110 Height = 25 Caption = 'FireDAC '#40664#35748#25490#24207 TabOrder = 2 OnClick = Button2Click end object FDConnection1: TFDConnection Left = 34 Top = 24 end object FDPhysSQLiteDriverLink1: TFDPhysSQLiteDriverLink Left = 143 Top = 24 end object FDGUIxWaitCursor1: TFDGUIxWaitCursor Provider = 'Forms' Left = 260 Top = 24 end object FDQuery1: TFDQuery Connection = FDConnection1 Left = 32 Top = 88 end object DataSource1: TDataSource DataSet = FDQuery1 Left = 132 Top = 88 end object FDSQLiteCollation1: TFDSQLiteCollation DriverLink = FDPhysSQLiteDriverLink1 CollationName = 'MyCollation' LocaleName = 'zh-CN' Left = 240 Top = 120 end

代码:

procedure TForm1.FormCreate(Sender: TObject);
var
  i: Integer;
  LCode: Integer;
begin
  {给 FDSQLiteCollation1 设定参数}
  FDSQLiteCollation1.DriverLink := FDPhysSQLiteDriverLink1;
//  FDSQLiteCollation1.CollationKind := scCompareString; //这是默认值(Unicode 不区分大小写,在 Win 下是调用 WinAPI.CompareString); 使用其他选项需要自定义排序规则
  FDSQLiteCollation1.LocaleName := 'zh-CN';
  FDSQLiteCollation1.Flags := [sfIgnoreCase];
  FDSQLiteCollation1.CollationName := 'MyCollation';     //下面所有的调用全要依赖这个名称
  FDSQLiteCollation1.Active := True;

  FDConnection1.Params.Add('DriverID=SQLite');
//  FDConnection1.Params.Add('OpenMode=CreateUTF8'); //这是默认值,可选 CreateUTF16(Unicode)

  {建立测试表,三个字段 str(汉字),code(汉字对应的 Unicode 值),id(添加顺序)}
  FDConnection1.ExecSQL('CREATE TABLE MyTable(str string(10),code integer,id integer)');
//  FDConnection1.ExecSQL('CREATE TABLE MyTable(str string(10) COLLATE MyCollation,id integer)'); //用在表设计时

  {添加测试数据数据}
  for i := 0 to 99 do
  begin
    LCode := Random($9FA5-$4E00);
    FDConnection1.ExecSQL('INSERT INTO MyTable(str,code,id) VALUES(:1,:2,:3)',[WideChar($4E00 + LCode),LCode,i+1]);
  end;

  FDQuery1.Open('SELECT * FROM MyTable'); //无排序
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
  FDQuery1.Open('SELECT * FROM MyTable ORDER BY str'); //SQLite 内置排序
end;

procedure TForm1.Button2Click(Sender: TObject);
begin
  FDQuery1.Open('SELECT * FROM MyTable ORDER BY str COLLATE MyCollation'); //FireDAC 默认排序
end;

测试效果图:

（编辑：李大同）

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