Convert positive data into negetive data (entire column) in Postgres Server
<p>The current data in my table is:</p>

<blockquote>
<pre><code>  a   b
---------  
 -1   5
 -11  2   
 -5  32
</code></pre>
</blockquote>

<p>My request is to convert every data of column a into negative value.</p>

<p>But how to update the positive values into the negative selecting the entire column?</p>