Conditionals and outputting tables
Assuming your example code, something along these lines will help...

{% if entry.yourTable | length %}
    &lt;table&gt;
    {% for row in entry.yourTable %}
    &lt;tr&gt;
       &lt;td&gt;{{ row.column1 }}&lt;/td&gt;&lt;td&gt;{{ row.column2 }}&lt;/td&gt;&lt;td&gt;{{ row.column3 }}&lt;/td&gt;
    &lt;/tr&gt; 
    {% endfor %}
    &lt;/table&gt;
{% endif %}


Here's the relevant section in the docs: Table fields