怎么实现嵌套表格的100%高度

如何实现嵌套表格的100%高度
<div style=" width:800px; height:600px;">
<table id="table1" width="100%" height="100%" border="1" cellspacing="0" cellpadding="0">
    <tr>
        <td style="height:120px;">&nbsp;</td>
        <td>&nbsp;</td>
        <td>&nbsp;</td>
    </tr>
    <tr>
        <td>&nbsp;</td>
        <td>
        
            <table id="table2" width="100%" height="100%" border="1" cellspacing="0" cellpadding="0">
                <tr>
                    <td>&nbsp;</td>
                    <td>&nbsp;</td>
                    <td>&nbsp;</td>
                </tr>
                <tr>
                    <td>&nbsp;</td>
                    <td>&nbsp;</td>
                    <td>&nbsp;</td>
                </tr>
                <tr>
                    <td>&nbsp;</td>
                    <td>&nbsp;</td>
                    <td>&nbsp;</td>
                </tr>