FireDAC 下的 Sqlite [8] - 自定义函数

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unit Unit1;

interface

uses
  Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics, Vcl.Controls, Vcl.Forms,
  Vcl.Dialogs, FireDAC.Stan.Intf, FireDAC.Stan.Option, FireDAC.Stan.Error, FireDAC.UI.Intf, FireDAC.Phys.Intf, FireDAC.Stan.Def,
  FireDAC.Stan.Pool, FireDAC.Stan.Async, FireDAC.Phys, FireDAC.Stan.ExprFuncs, FireDAC.VCLUI.Wait, FireDAC.Stan.Param, FireDAC.DatS,
  FireDAC.DApt.Intf, FireDAC.DApt, Vcl.Grids, Vcl.DBGrids, Data.DB, FireDAC.Comp.DataSet, FireDAC.Comp.Client, FireDAC.Comp.UI,
  FireDAC.Phys.SQLite, Vcl.StdCtrls, FireDAC.Phys.SQLiteWrapper;

type
  TForm1 = class(TForm)
    FDConnection1: TFDConnection;
    FDPhysSQLiteDriverLink1: TFDPhysSQLiteDriverLink;
    FDGUIxWaitCursor1: TFDGUIxWaitCursor;
    FDQuery1: TFDQuery;
    DataSource1: TDataSource;
    DBGrid1: TDBGrid;
    Button1: TButton;
    Button2: TButton;
    FDSQLiteFunction1: TFDSQLiteFunction;
    FDSQLiteFunction2: TFDSQLiteFunction;
    procedure FormCreate(Sender: TObject);
    procedure Button1Click(Sender: TObject);
    procedure Button2Click(Sender: TObject);
    procedure FDSQLiteFunction1Calculate(AFunc: TSQLiteFunctionInstance; AInputs: TSQLiteInputs; AOutput: TSQLiteOutput; var AUserData: TObject);
    procedure FDSQLiteFunction2Calculate(AFunc: TSQLiteFunctionInstance; AInputs: TSQLiteInputs; AOutput: TSQLiteOutput; var AUserData: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

procedure TForm1.FormCreate(Sender: TObject);
const
  strTable = ‘CREATE TABLE MyTable(姓名 string(10), 语文 Integer, 数学 Integer, 英语 Integer)‘; // 建一个学生成绩表
begin
  { 建立一个成绩表, 并插入测试数据 }
  FDConnection1.Params.Add(‘DriverID=SQLite‘);
  FDConnection1.ExecSQL(strTable);
  FDQuery1.ExecSQL(‘INSERT INTO MyTable(姓名, 语文, 数学, 英语) VALUES(:1, :2, :3, :4)‘, [‘张三‘, 66, 77, 88]);
  FDQuery1.ExecSQL(‘INSERT INTO MyTable(姓名, 语文, 数学, 英语) VALUES(:1, :2, :3, :4)‘, [‘李四‘, 77, 88, 99]);
  FDQuery1.Open(‘SELECT * FROM MyTable‘);

  { 分别给两个 TFDSQLiteFunction 设定参数 }
  FDSQLiteFunction1.DriverLink := FDPhysSQLiteDriverLink1;
  FDSQLiteFunction1.FunctionName := ‘MyFun1‘; // 函数名
  FDSQLiteFunction1.ArgumentsCount := 3; // 函数的参数个数
  // FDSQLiteFunction1.OnCalculate := FDSQLiteFunction1Calculate; //在设计时建立 OnCalculate 事件更方便
  FDSQLiteFunction1.Active := True;

  FDSQLiteFunction2.DriverLink := FDPhysSQLiteDriverLink1;
  FDSQLiteFunction2.FunctionName := ‘MyFun2‘;
  FDSQLiteFunction2.ArgumentsCount := 3;
  // FDSQLiteFunction2.OnCalculate := FDSQLiteFunction2Calculate; //在设计时建立 OnCalculate 事件更方便
  FDSQLiteFunction2.Active := True;
end;

{ 调用 MyFun1 }
procedure TForm1.Button1Click(Sender: TObject);
begin
  FDQuery1.Open(‘SELECT 姓名, MyFun1(语文, 数学, 英语) AS 总分 FROM MyTable‘);
end;

{ 调用 MyFun2 }
procedure TForm1.Button2Click(Sender: TObject);
begin
  FDQuery1.Open(‘SELECT 姓名, MyFun2(语文, 数学, 英语) AS 平均分 FROM MyTable‘);
end;

{ 函数 MyFun1 的定义: 算总分 }
procedure TForm1.FDSQLiteFunction1Calculate(AFunc: TSQLiteFunctionInstance; AInputs: TSQLiteInputs; AOutput: TSQLiteOutput; var AUserData: TObject);
begin
  AOutput.AsInteger := AInputs[0].AsInteger + AInputs[1].AsInteger + AInputs[2].AsInteger;
end;

{ 函数 MyFun2 的定义: 算平均分 }
procedure TForm1.FDSQLiteFunction2Calculate(AFunc: TSQLiteFunctionInstance; AInputs: TSQLiteInputs; AOutput: TSQLiteOutput; var AUserData: TObject);
begin
  AOutput.AsFloat := (AInputs[0].AsInteger + AInputs[1].AsInteger + AInputs[2].AsInteger) / 3;
end;

end.

FireDAC 下的 Sqlite [8] - 自定义函数,布布扣,bubuko.com

FireDAC 下的 Sqlite [8] - 自定义函数

标签：style   c   class   blog   tar   ext   

原文地址：http://www.cnblogs.com/del/p/3746505.html