title: How to extract the year of a DATE and insert it in a new column?
body: <p>I have a column in my table which contains DATEs and I need to keep only the YEAR (=> in a NUMBER or INT type)</p>
  
  <p>My idea was to add a column and try something like this :</p>
  
  <pre><code>UPDATE myTable SET newColumn=(
  select to_number(to_char(oldColumn.year, 'yyyy')) from myTable)
  </code></pre>
  
  <p>But I get this error :</p>
  
  <blockquote>
    <p>single-row subquery returns more than one row</p>
  </blockquote>
  
  <p>Could you help?!?</p>