<tr>
        <td colspan="3" align="left" bgcolor="#FFFFFF">
        <select id="attr1" name="attr1"><option selected value="0">请选择</option></select>
        <select id="attr2" name="attr2"><option selected value="0">请选择</option></select>
        <input type= "button" name= "button" value= "添加" onclick="ClickAddAttr();" />
        </td>
        </tr>
加载网页后，数据库里的记录自动添加到下拉框，怎么修改上面的代码让他自动加载到复选框？