ADO多线程数据库查询

{ADO查询多线程单元}

unit ADOThread;

interface

uses

  Classes,StdCtrls,ADODB;

type TADOThread = class(TThread)

  private { Private declarations }

  FListBox:TListBox;

  FLabel:TLabel;

  ConnString:WideString;

  FSQLString:string;

  sl:TStrings;

  procedure UpdateCount;

  protected procedure Execute; override;

  public constructor Create(SQL:string;LB:TListBox;Lab:TLabel);

end;

implementation

uses

  unit1,SysUtils,ActiveX;

  { TADOThread }

constructor TADOThread.Create(SQL: string; LB: TListBox;Lab:TLabel);

begin

  ConnString:=Form1.con1.ConnectionString;

  FListBox:=LB;

  FLabel:=Lab;

  FSQLString:=SQL;

  Inherited Create(False);

end;

procedure TADOThread.Execute;

var

  Qry:TADOQuery;

  i:Integer;

begin { Place thread code here }

  FreeOnTerminate:=True;

  sl:=TStringList.Create;

  CoInitialize(nil); //必须调用（需Uses ActiveX）

  Qry:=TADOQuery.Create(nil);

  try

    Qry.ConnectionString:=ConnString; //必须有自己的连接

    Qry.Close;

    Qry.SQL.Clear;

    Qry.SQL.Add(FSQLString);

    Qry.Open;

    FListBox.Clear;

    for i :=  to  do //为了执行久点重复历遍数据集101次

    begin

      Qry.First;

      while not Qry.Eof And not Terminated do

      begin

        //FListBox.AddItem(Qry.Fields[0].asstring,nil);

        //FListBox.Items.Add(Qry.Fields[0].asstring);

        sl.Add(Qry.Fields[].asstring);

        //如果不调用Synchronize，会出现Canvas Does NOT Allow Drawing

        //Synchronize(UpdateCount);

        Qry.Next;

      end;

      //Qry.First;

      //FListBox.AddItem('*******',nil);

      //Synchronize(UpdateCount);

    end;

    Synchronize(UpdateCount);

  finally

    sl.Free;

    Qry.Free;

  end;

  CoUninitialize;

end;

procedure TADOThread.UpdateCount;

begin

  //FLabel.Caption:=IntToStr(FListBox.Items.Count);

  FListBox.Items.Assign(sl);

  FLabel.Caption:=IntToStr(sl.Count);

end;

end.

unit Unit1;

interface

uses

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

  Dialogs, DB, ADODB, StdCtrls;

type

  TForm1 = class(TForm)

    lbl1: TLabel;

    lbl2: TLabel;

    lbl3: TLabel;

    lst1: TListBox;

    lst2: TListBox;

    lst3: TListBox;

    cbb1: TComboBox;

    cbb2: TComboBox;

    cbb3: TComboBox;

    btn1: TButton;

    qry1: TADOQuery;

    con1: TADOConnection;

    procedure FormCreate(Sender: TObject);

    procedure btn1Click(Sender: TObject);

  private

    { Private declarations }

  public

    { Public declarations }

  end;

var

  Form1: TForm1;

implementation

{$R *.dfm}

uses ADOThread;

procedure TForm1.FormCreate(Sender: TObject);

var

  strSQL:string;

begin

  strSQL:='select * from tb_student';

  qry1.Close;

  qry1.SQL.Clear;

  qry1.SQL.Add(strSQL);

  qry1.Open;

  cbb1.Clear;

  cbb2.Clear;

  cbb3.Clear; //将客户Company和相关CustNo填到ComboBox中

  while not qry1.Eof do

  begin

    //cbb1.AddItem(qry1.Fields[1].asString, TObject(qry1.Fields[0].AsInteger));

    cbb1.Items.Add(qry1.fieldbyname('smc').AsString);

    qry1.Next;

  end;

  cbb2.Items.Assign(cbb1.Items);

  cbb3.Items.Assign(cbb1.Items); // 默认选中第一个

  cbb1.ItemIndex := ;

  cbb2.ItemIndex := ;

  cbb3.ItemIndex := ;

end;

procedure TForm1.btn1Click(Sender: TObject);

const

  SQL_CONST='select sxm from tb_student where sxm';

  var c1,c2,c3:Integer; s1,s2,s3:string;

begin //取得三个选择框客户的编码

  s1:=SQL_CONST+QuotedStr(cbb1.Text);

  s2:=SQL_CONST+QuotedStr(cbb2.Text);

  s3:=SQL_CONST+QuotedStr(cbb3.Text);//三个线程同时查询

  TADOThread.Create(s1,lst1,lbl1);

  TADOThread.Create(s2,lst2,lbl2);

  TADOThread.Create(s3,lst3,lbl3);

end;

end.