Regular Expression and PL/SQL help

Question

I am using Oracle 9i, does 9i support regular expression? What functions are there?
My problem is the birth_date column in my database comes from teleform ( a scan program that reads what people wrote on paper), so the format is all jacked up.... 50% of them are 01/01/1981, 10% are 5/14/1995, 10% are 12/5/1993, 10% are 1/1/1983, 10% are 24-JUL-98. I have never really used regular expression and pl/sql, can anybody help me convert all of them to 01/01/1998?
Does Oralce 9i support regular expression? What can I do if oralce 9i does not support regular expression? Thank you very much in advance.

Answer 1

9i doesn't support regular expressions (at least not in the 10g regular expressions sense. There is an OWA_PATTERN_MATCH package that has some facilities for regular expressions). But it doesn't look like this is a regular expressions problem.
Instead, this is probably a case where you need to
- enumerate the format masks you want to try
- determine the order you want to try them
- write a small function that tries each format mask in succession until one matches.
Of course, there is no guarantee that you'll ever be able to convert the data to the date that the user intended because some values will be ambiguous. For example, 01/02/03 could mean Feb 1, 2003 or Jan 2, 2003 or Feb 3, 2001 depending on the person who entered the data.
Assuming you can define the order, your function would just try each format mask in turn until one generated a valid date, i.e.
BEGIN
  BEGIN
    l_date := TO_DATE( p_string_value, format_mask_1 );
    RETURN l_date;
  EXCEPTION
    WHEN OTHERS THEN
      NULL;
  END;
  BEGIN
    l_date := TO_DATE( p_string_value, format_mask_2 );
    RETURN l_date;
  EXCEPTION
    WHEN OTHERS THEN
      NULL;
  END;
  BEGIN
    l_date := TO_DATE( p_string_value, format_mask_3 );
    RETURN l_date;
  EXCEPTION
    WHEN OTHERS THEN
      NULL;
  END;
  BEGIN
    l_date := TO_DATE( p_string_value, format_mask_N );
    RETURN l_date;
  EXCEPTION
    WHEN OTHERS THEN
      NULL;
  END;
  RETURN NULL;
END;Justin