title: Regex in Oracle PL/SQL to remove unwanted characters from a string containing a phone number
body: <p>I need to remove the characters -, +, (, ), and space from a string in Oracle. The other characters in the string will all be numbers.
  The function that can do this is REGEXP_REPLACE. I need help writing the correct regex.</p>
  
  <p>Examples:
  string '23+(67 -90' should return '236790'
  string '123456' should return '123456'</p>