SQL Average values from different rows
<p><a href="https://i.stack.imgur.com/b3DLk.png" rel="nofollow">Share Weights to Average Share Weights</a></p>

<p>Please refer to the image above.</p>

<p>I currently have the share weights table in SQL. I'd like to produce the average share weights table. The average share weight in each cell is calculated by averaging the value for that asset in that year with the value for that asset in the previous year. </p>

<p>For example:</p>

<ul>
<li>2011 asset 1 (5.5) was calculated by averaging 6 (2010 asset 1) and 5 (2011 asset 1).</li>
<li>2010 row doesn't have any average share weights because there is no 2009.</li>
<li>2014 asset 3 (7) was calculated by averaging 1 (2013 asset 3) and 13 (2014 asset 3).</li>
</ul>

<p>I'd appreciate any help. Thanks!</p>