父table样式:
border:1px solid #000;
border-spacing:0;
border-collapse:collapse;
子table样式:
border-style:hidden
<style>table {border-collapse: collapse;width:100%;}tr,th,td {padding: 0;border: 1px solid;text-align: center;}</style><table><tr><th>表头1</th><th>表头2</th><th>表头3</th></tr><tr><td><table style="border-style:hidden"><tr><td>-</td><td>-</td><td>-</td></tr><tr><td>-</td><td>-</td><td>-</td></tr></table></td><td>表格2</td><td>表格3</td></tr></table>