线程异常问题

[zgwu]

程序很简单，请问为什么会有异常？

unit Unit1;

interface

uses
Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,unit2,
Db, DBTables;

type
TForm1 = class(TForm)
Query1: TQuery;
procedure FormCreate(Sender: TObject);
private
{ Private declarations }
public
{ Public declarations }
end;
type
ThreadGetCMM = class(TThread)
tQuery:TQuery;
public
procedure Execute; override;
end;
var
Form1: TForm1;

implementation

{$R *.DFM}

procedure TForm1.FormCreate(Sender: TObject);
var myThreadGetCMM:ThreadGetCMM;

begin
myThreadGetCMM:=ThreadGetCMM.Create(false);
myThreadGetCMM.FreeOnTerminate:=true;

end;


procedure ThreadGetCMM.Execute;
begin
try
tQuery.Close;
tQuery.ParamByName('empid').AsString:='1';
tQuery.ParamByName('sYear').AsString:='1';
tQuery.ParamByName('sMonth').AsString:='1';
tQuery.Open;
except
ShowMessage('线程异常');
end

end;

end.

[wgjsoft]

procedure ThreadGetCMM.Execute;
begin
try
query:=Tquery.create(nil);
Query.Close;
query.sql.clear;
query.sql.add('......');
Query.ParamByName('empid').AsString:='1';
Query.ParamByName('sYear').AsString:='1';
tQuery.ParamByName('sMonth').AsString:='1';
tQuery.Open;
except
ShowMessage('线程异常');
query.free;
end

end;
客户请求时自动产生一个query来操作数据库

[wzrlover]

SQL语句呢？参数类型是否正确