使用Oracle SQL查找字符串中最长的单词

I would like to find the longest word in a varchar2 (in a string) in an Oracle query. In some situations I would split the string into separate words in a table, then aggregation functions could solve it (e.g. once I have max(length(my_field) I can track down the longest word(s)).I would like to find the longest word in a varc