title: Subtract month from date column
body: <p>I would like to subtract one month from a date column in Amazon Redshift (a fork of PostgreSQL 8.0.2). </p>
  
  <p>So for each date column in a table, it will add another column date_minus_a_month.</p>
  
  <p>I tried this code</p>
  
  <pre><code>Select date,date::date -interval '1 month'
  from table
  </code></pre>
  
  <p>and received  an  error:  </p>
  
  <blockquote>
    <p>Interval values with month or year parts are not supported.</p>
  </blockquote>
  
  <p>Does anyone have a solution for this?</p>