title: Postgres selecting only columns that meet a condition
body: <p>If I have a database table <code>t1</code> that has the following data:</p>
  
  <p>How can I select just those columns that contain the term "false"</p>
  
  <pre><code> a   |   b   |  c   |  d   
  ------+-------+------+------
   1    | 2     | 3    | 4
   a    | b     | c    | d
   5    | 4     | 3    | 2
   true | false | true | true
   1    | 2     | 3    | 4
   a    | b     | c    | d
   5    | 4     | 3    | 2
   true | false | true | true
   1    | 2     | 3    | 4
   a    | b     | c    | d
   5    | 4     | 3    | 2
   true | false | true | true
  </code></pre>
  
  <p>Thanks</p>