在应用程序中出现提示：table unknown logintable unknown ISC error 336397208，请问怎么回事？

在saide.fdb中建立了一个用于登陆的数据表logintable，UserID 为自增 SQL语句是：create table table(userid int,UserName varchar(20),password varchar(20)) 接着希望向logintable表中插入数据，出现若干错误，代码如下：
unit Unit1;interfaceuses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls, Grids, DBGrids, DB, DBClient, SimpleDS, SqlExpr, MIDASLIB,
  DBXpress, FMTBcd, ComCtrls;type
  TForm1 = class(TForm)
    SQLConnection1: TSQLConnection;
    SimpleDataSet1: TSimpleDataSet;
    datasource1: TDataSource;
    btnConnect: TButton;
    btnCommit: TButton;
    btnQuery: TButton;
    DBGrid1: TDBGrid;
    lbl1: TLabel;
    Edit1: TEdit;
    Edit2: TEdit;
    Edit3: TEdit;
    Button1: TButton;
    SQLQuery1: TSQLQuery;
    DateTimePicker1: TDateTimePicker;
    Edit4: TEdit;
    Edit5: TEdit;
    Label1: TLabel;
    Label2: TLabel;
    Button2: TButton;
    Button3: TButton;
    procedure btnConnectClick(Sender: TObject);
    procedure btnQueryClick(Sender: TObject);
    procedure btnCommitClick(Sender: TObject);
    procedure FormCreate(Sender: TObject);
    procedure Button1Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;var
  Form1: TForm1;implementation{$R *.dfm}
procedure TForm1.btnQueryClick(Sender: TObject);
begin
  if not sqlConnection1.Connected then
  begin
    showmessage('请先连接');
    exit;
  end;
    
  SimpleDataSet1.DataSet.CommandText:='select * from logintable';
  simpleDataSet1.Open;
end;procedure TForm1.btnCommitClick(Sender: TObject);
begin
  if simpleDataSet1.ApplyUpdates(0)>0 then
    showmessage('提交数据不成功!')
  else
    showmessage('提交数据成功!');
end;procedure TForm1.FormCreate(Sender: TObject);
begin
  if SQLConnection1.Connected=true then
    SQLConnection1.Connected:=false;
  SQLConnection1.Params.Clear;
  SQLConnection1.Params.Values['user_name']:='sysdba';
  SQLConnection1.Params.values['password']:='masterkey';
  sqlConnection1.Params.Values['SQLDialect']:='3';
  SQLConnection1.Params.Values['database']:=extractfilepath(paramstr(0))+'data\saide.fdb';
  SQLConnection1.Connected:=true;
end;procedure TForm1.Button1Click(Sender: TObject);
begin
with simpleDataSet1 do 
begin SQLQuery1.SQL.Text:='insert into logintable (UserName,password) values ('''+Quotedstr(Edit1.Text)+''','''+Quotedstr(Edit2.Text)+''')'; SQLQuery1.ExecSQL(False);
 SimpleDataSet1.Refresh;
end;
begin
  if simpleDataSet1.ApplyUpdates(0)>0 then
    showmessage('提交数据不成功!')
  else
    
end;
end;
end.
//点击 TForm1.btnQueryClick，出现：table unknown logintable unknown ISC error 336397208
//点击 TForm1.Button1Click，出现：
Token unknown -line 1,column 34 password
//点击 TForm1.btnCommitClick，出现：
SimpleDataSet1:Cannot perform this operation on a closed dataset.