How can I simplify this statement using regular expressions?

Please suppose you have the following st开发者_JS百科atement stored in a VARCHAR2:

UPDATE PLUTO SET FIELD1='',FIELD2='',FIELD3='TIGER',FIELD4='',FIELD5='SCOTT';

I would like to write a regular expression that simplifies the previous statement, by removing all the updates setting to NULL, because they are useless (NULL is the default statement), as follows:

UPDATE PLUTO SET FIELD3='TIGER', FIELD5='SCOTT';

Could you help me?

I have never been so good with regular expressions...!!

SELECT
REGEXP_REPLACE(
 REGEXP_REPLACE(
  'UPDATE PLUTO SET FIELD1='''',FIELD2='''',FIELD3=''TIGER'',FIELD4='''',FIELD5=''SCOTT'',FIELD9='''';',
  '(FIELD[0-9]+=(?'''',*))','') ,
  '[, ]+;',';')
from dual

how's this? it will remove all FIELD#='' (with or without final ,)

here's a regular expression cheat sheet: http://psoug.org/snippet.htm/Regular_Expressions_Regex_Cheat_Sheet_856.htm?PHPSESSID=7238be874ab99d0731a9da64f2dbafd8 and good resource on Oracle's Regular Expression http://psoug.org/snippet/Regular-Expressions---REGEXP_REPLACE_882.htm

I believe this should get you what you want, but there may be a better way, as I am not the best with regexp either:

regexp_replace(regexp_replace(field, 'FIELD[0-9]+=''''[,]*', ''), '[, ]+;', ';')