title: substr Error -- ORA-01722:invaild number separate string
body: <p>I am trying to separate first and last name . I have a column called 'Fullname' and it has first and last name and a comma all in one column. I've tried the below but I get an error " its not a valid number". When I remove the comma it works, so I am not sure how to incorporate a comma in the formula so it can work. </p>
  
  <p>,<code>substr(Fullname,1,',') as Lastname</code>
  ,<code>substr(Fullname,',','  ') as Firstname</code></p>
  
  <pre><code>Column 
  
  Fullname
  Brown,John N
  Green,Julie T
  
  
  Desired results
  Lastname    FirstName
  Brown        John
  Green        Julie
  </code></pre>