title: PostgreSQL get items from last 12 hours
body: <p>I have the following query to get what I want in PHP file, it does it's job except the <code>WHERE</code> part. I need to get items that have <code>date_time1</code> column for last 12 hours.</p>
  
  <pre><code>SELECT p.*, t.* 
  FROM posts AS p 
  LEFT JOIN posted_tweets AS t 
  ON p.a_id = t.p_id
  WHERE p.date_time1 &gt;= now() AND t.date_time =
  ( 
      SELECT MAX(date_time) 
      FROM posted_tweets AS t2 
      WHERE t2.p_id = t.p_id
  )
      OR t.date_time IS NULL 
  </code></pre>
  
  <p>How exactly should I edit <code>p.date_time1 &gt;= now()</code> part to reach my aim? Thanks.</p>