title: how to extract specific word from string in Postgres
body: <p>Product name contains words deliminated by space.
  First word is size second in brand etc.</p>
  
  <p>How to extract those words from string, e.q how to implement query like:</p>
  
  <pre><code>select
    id,       
    getwordnum( prodname,1 ) as size,
    getwordnum( prodname,2 ) as brand
    from products
  where ({0} is null or getwordnum( prodname,1 )={0} ) and
      ({1} is null or getwordnum( prodname,2 )={1} )
  
  
  create table product ( id char(20) primary key, prodname char(100) );
  </code></pre>
  
  <p>How to create getwordnum() function in Postgres or should some substring() or other function used directly in this query to improve speed ?</p>