title: How to handle invalid_identifier exception in pl/sql?
body: <p>i need to check if a certain SELECT statement includes a field (column) that doesn't exists in a table, for example:</p>
  
  <p>select col1, col2, col3 from table1</p>
  
  <p>if col1 dosen't exists i want to show "missing field", instead for the user to get an invalid identifier error.</p>
  
  <p>what is my best and short option to do this?</p>