Count Distinct with PostgreSQL
<p>I am trying to change the count DISTINCT portion of the query below, because the current query returns WINDOW definition is not supported.  What is most seamless way to do this calc using PostgreSQL?  Thank you.</p>

<pre><code>SELECT transaction_date, brand, Description, Amount, newval
into temp.table
FROM (SELECT transaction_date, brand, Description, Amount,
         (Amount / count(DISTINCT unique_mem_id) over (partition by to_char(transaction_date, 'YYYY-MM'),brand
         )) as newval
  FROM source.table
 )
WHERE DESCRIPTION iLIKE '%Criteria%';
</code></pre>