Find unique characters in field (of all entries) (no replies)

Hi, are there any easy and efficient ways to get a distinct "sum" of all the characters used in all entries, in a field?

E.g.:

Entries with field `characters`, with values: "abc", "acbd", "cbde", should return: "abcde"

I'm working on a function, but it seems to be inefficient, would be grateful of any tips.