title: Remove non-date values from a varchar column in oracle
body: <p>In a table called customers I have a varchar2 column(financial_month).<br>
  This column is supposed to be a date column but since it is a varchar2 column and due to some wrong coding, there are many data which aren't in date format.<br>
  For eg: 0.15 has been stored in one record and many other wrong entries.</p>
  
  <p>Now I want to eliminate all the wrong entries.<br>
  What process should I follow?<br>
  I have no clue whatsoever. I am not able to identify the wrong entries as well. The only thing I know is that there are more than 1000 wrong entries. </p>
  
  <p>How to remove all the wrong entries from this column?</p>