Removing redundant itemsets

Hi all,
I have a plain sql problem (didn't know where else to post it).
I have a list of transactions (market basket) and I would like to select
non redundant longest possible patterns by eliminating
(creating/populating other table to contain only non redandant itemsets)
transactions having item lists which are fully included in at least one
other transaction.

(Am assuming all the items of all the transactions have met the minimum
support currently set at 1)

Below is a sample case, table schema and data(DDL and DML)

Transaction Itemset
'100' 'a','b','c','d'
'200' 'c','d'
'300' 'a','c','e'
'400' 'e','d'

On successful removal out of 'redanduant' or smaller transactions having
items contained in totality by at least one other transaction, the
transaction '200' would be weeded out as it's itemset {'c','d'} is
contained in '100' {'a','b','c','d'} transaction.

drop sequence if exists togo_seq cascade;
create sequence togo_seq;
drop table if exists togo cascade;
create table togo
(
id integer not null default nextval('togo_seq')
,tid char(3) not null
,item char(1) not null
,primary key(id)
,unique(tid,item)
)
;
insert into togo(tid,item)values('100','b');
insert into togo(tid,item)values('100','a');
insert into togo(tid,item)values('100','c');
insert into togo(tid,item)values('100','d');
insert into togo(tid,item)values('200','c');
insert into togo(tid,item)values('200','d');
insert into togo(tid,item)values('300','a');
insert into togo(tid,item)values('300','c');
insert into togo(tid,item)values('300','e');
insert into togo(tid,item)values('400','e');
insert into togo(tid,item)values('400','d');

Allan.