jquery选择器的问题

现在的代码实现的效果是：当鼠标移动到表格的某一行时，该行的背景色就变为黄色。
问题是：当鼠标移动到表格的最后一行（该行嵌套了一个表格）时，我不想让该行变色。这个怎么写？

html关键代码：
         <style type="text/css">
            .style1
            {
                background-color:yellow;
            }
        </style
                <table id="table1" style="width:50%; border:blue 1px solid; text-align:center;">
                    <tr>
                        <th>姓名</th>
                        <th>年龄</th>
                        <th>QQ</th>
                        <th>Email</th>
                    </tr>
                    <tr>
                        <td>张三</td>
                        <td>22</td>
                        <td>123456</td>
                        <td>[email protected]</td>
                    </tr>
                    <tr>
                        <td>张三</td>
                        <td>22</td>
                        <td>123456</td>
                        <td>[email protected]</td>
                    </tr>
                    <tr>
                        <td colspan="4">
                            <table>
                            <table id="table2" style="border:red 1px solid; width:50%;">
                                <tr>
                                    <td colspan="4">路人甲(id=table2)</td>
                                </tr>
                            </table>
                            </table>
                        </td>
                    </tr>
                </table>
jquery代码：
    
     $(document).ready ( function() {
                             $("#table1 tr").mouseover ( function() {
                    $(this).addClass("style1");
          }
                    ).mouseout ( function() {
                                     $(this).removeClass("style1");
  }
                    )                    ;