distinct subset query

Given a relation of sets (in 1NF), return all the distinct sets.

For example, given

{a},{a,b},{a,b}

encoded as

set# element
---- -------

1     a
1     b
2     a
2     b
3     a

The expected return is

min
set# element
---- -------

1     a
1     b
3     a

Is it a well known query, and how to express it in SQL? Received on Fri Jul 14 2006 - 14:58:48 CDT