SQL & PL/SQL :: Finding UNIQUE Combination

I have contents like below:

BREAD,BISCUIT
BREAD,MILK,BISCUIT
COKE,MILK
MILK,SUGAR

Now combination from each row will be like below (Just for understanding):

BREAD,BISCUIT --> [COMBINATION] {BISCUIT} {BREAD} {BISCUIT,BREAD}
BREAD,MILK,BISCUIT --> [COMBINATION] {BISCUIT} {BREAD} {MILK} {BISCUIT,BREAD} {BISCUIT,MILK} {BREAD,MILK} {BISCUIT,BREAD,MILK}
COKE,MILK --> [COMBINATION] {COKE} {MILK} {COKE,MILK}
MILK,SUGAR --> [COMBINATION] {MILK} {SUGAR} {MILK,SUGAR}

Now the ultimate aim is to find unique combinations (even if the same combination is present in different rows, we have to consider it as one combination), along with its frequency, result will be like below:

BISCUIT [occurence in 2 transactions and total 4 transactions] = 2/4 = .5
BREAD [occurence in 2 transactions and total 4 transactions] = 2/4 = .5
COKE [occurence in 1 transactions and total 4 transactions] = 2/4 = .25
MILK = 3/4 = .75

[Code]....

writing query to find unique combination like above? What I have tried is as below:

create table test (row_no number, col_no number, item varchar2(50))
/

insert into test values (1,1,'BREAD');
insert into test values (1,2,'BISCUIT');
insert into test values (2,1,'BREAD');

[Code]....

But I am not able to form the exact query. let me know if this can't be done through a single query.