procedure TForm1.Button1Click(Sender: TObject);
begin
Query1.Close;{close the query}
//assign new SQL expression
Query1.SQL.Clear;
Query1.SQL.Add ('Select EmpNo, FirstName, LastName');
Query1.SQL.Add ('FROM Employee.db');
Query1.SQL.Add ('WHERE Salary > ' + Edit1.Text);
Query1.Open; {open query + display data}
end;